bluewave

Enjoying the cooler weather here as my area made it to #2 on the all-time 90° day list this year at 15 days. Time Series Summary for NEW HAVEN TWEED AP, CT - Jan through Dec Top 5 years for 90° days Click column heading to sort ascending, click again to sort descending. 1 2022 17 0 2 2025 15 132 3 2010 14 0 4 1977 13 100 5 2021 12 0 - 2020 12 2 - 2012 12 3

It’s difficult for many of us who are cold and snow enthusiasts to understand why so many people choose to move to a place like Phoenix with such intense heat. I would enjoy visiting that region during some of the cooler times of the year since the Desert Southwest is one of the most beautiful parts of the country. You wonder how much more heat and drought it would take to actually slow the influx of new people into the area. In the mean time I hope they do all they can to try and expand the trees and shade.

The only stations I could find that made it to 100° from July to September in 1983 were in an around Philly. Monthly Data for July 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. DE NEWARK AG FARM COOP 105 NJ MOORESTOWN 4 E COOP 102 PA NORRISTOWN COOP 101 MD DENTON 2 E COOP 100 PA MARCUS HOOK COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA PHILADELPHIA WBAN 100 PA DREXEL UNIV COOP 100 NJ ATLANTIC CITY INTL AP WBAN 100 NJ INDIAN MILLS 2 W COOP 100 Monthly Data for August 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. MD CHESTERTOWN COOP 101 MD MILLINGTON 1 SE COOP 101 PA PHOENIXVILLE 1 E COOP 101 PA PHILADELPHIA WBAN 101 PA DREXEL UNIV COOP 101 MD CENTREVILLE COOP 100 DE BRIDGEVILLE 1 NW COOP 100 MD DENTON 2 E COOP 100 DE NEWARK AG FARM COOP 100 PA MARCUS HOOK COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA NORRISTOWN COOP 100 NJ HAMMONTON 1 NE COOP 100 NJ INDIAN MILLS 2 W COOP 100 Monthly Data for September 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. PA PHILADELPHIA WBAN 102 NJ HAMMONTON 1 NE COOP 102 NJ EWING 3 WNW COOP 101 MD CENTREVILLE COOP 100 MD CHESTERTOWN COOP 100 DE BRIDGEVILLE 1 NW COOP 100 DE NEWARK AG FARM COOP 100 DE MIDDLETOWN 3 E COOP 100 PA MARCUS HOOK COOP 100 NJ SHILOH COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA NORRISTOWN COOP 100 PA READING 4 NNW COOP 100 NJ AUDUBON COOP 100 NJ LAMBERTVILLE COOP 100

The peak heat in 2010 was focused in July like we typically see. The most unusual heat in 1983 was the record heatwave coming so late on September 10th-11th. Could be related to the drought which developed that summer. That may be the last time that Queens reached 100° so late in the season. Monthly Data for July 2010 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. NY MINEOLA COOP 108 NY WANTAGH CEDAR CREEK COOP 107 NJ CANOE BROOK COOP 107 NJ RINGWOOD COOP 106 NJ HARRISON COOP 106 CT DANBURY COOP 104 NJ CRANFORD COOP 104 NY WEST POINT COOP 103 NJ TETERBORO AIRPORT COOP 103 NY SHIRLEY BROOKHAVEN AIRPORT WBAN 103 NJ NEWARK LIBERTY INTL AP WBAN 103 NY LAGUARDIA AIRPORT WBAN 103 NY NY CITY CENTRAL PARK WBAN 103 NJ TETERBORO AIRPORT WBAN 103 Data for September 10, 1983 through September 11, 1983 Click column heading to sort ascending, click again to sort descending. NJ PLAINFIELD COOP 100 NY NEW YORK LAUREL HILL COOP 100 NJ CRANFORD COOP 99 NJ NEWARK LIBERTY INTL AP WBAN 99 NY NY WESTERLEIGH STAT IS COOP 99 NY NY CITY CENTRAL PARK WBAN 99 NY WESTBURY COOP 99 NJ JERSEY CITY COOP 98 NJ CANOE BROOK COOP 98 NY NEW YORK AVE V BROOKLYN COOP 98 NJ ESSEX FELLS SERVICE BLDG COOP 98 NY DOBBS FERRY-ARDSLEY COOP 98 NY WEST POINT COOP 98 NY GARNERVILLE COOP 98 NY JFK INTERNATIONAL AIRPORT WBAN 98 NY VANDERBILT MUSEUM COOP 98 NY WESTCHESTER CO AP WBAN 98 CT NEW HAVEN COOP 98 Data for September 10, 1983 through September 11, 1983 Click column heading to sort ascending, click again to sort descending. PA PHILADELPHIA WBAN 102 NJ EWING 3 WNW COOP 101 MD CENTREVILLE COOP 100 MD CHESTERTOWN COOP 100 DE BRIDGEVILLE 1 NW COOP 100 DE NEWARK AG FARM COOP 100 DE MIDDLETOWN 3 E COOP 100 PA MARCUS HOOK COOP 100 NJ SHILOH COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA READING 4 NNW COOP 100 NJ AUDUBON COOP 100 NJ LAMBERTVILLE COOP 100

So far we have had 4 summers since 2017 with the highest temperature of the year occurring in June or not getting surpassed later in the summer. This is a first for our area over such a short period of time. It makes years like 1953 even more challenging to match with 105° heat in September. Since heat getting established early peaks before we get to August and September. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ Jun-Aug Max Temps Click column heading to sort ascending, click again to sort descending. 2025 103 101 96 103 2021 103 97 99 103 2011 102 108 98 108 1994 102 99 95 102 1993 102 105 100 105 1952 102 98 92 102 1943 102 95 97 102 1988 101 101 99 101 1966 101 105 95 105 2024 100 99 100 100 1959 100 93 96 100 1953 100 99 102 102 1934 100 98 90 100 1923 100 99 92 100 2017 99 98 93 99 Monthly Highest Max Temperature for LAGUARDIA AIRPORT, NY Jun-Aug Max Temps Click column heading to sort ascending, click again to sort descending. 2025 101 100 91 101 2017 101 98 91 101 1952 101 97 90 101 2021 100 96 98 100 2008 100 97 88 100 1988 99 99 97 99 1956 99 94 92 99 1943 99 91 93 99 2012 98 101 93 101 1959 98 91 94 98 2024 97 97 95 97

Sea breeze activity really depends on the pattern. But I agree that the more weather stations we have the better. 2010 was the greatest sea breeze outlier that I ever saw living in Long Beach. Much of the spring into early fall was dominated by westerly flow. So it was the warmest summer on record to this day in Long Beach and other areas especially along the coastal plain. Most of the time anyone south of the LIE and Northern State usually get sea breezes. But this is more enhanced south of the Southern State and Sunrise Highway. So once north of the immediate South Shore the sea breeze has less cooling influence. Though it does have some effect especially by later in the day.

Maybe with the depth of the trough for early next week we can get another opportunity for some much needed rainfall.

My area east of HVN has been at +0.5 for August so far. So a nice step down from the record heat in June and July. The last few days here have been the coolest of the month so far.

Some localized heavier amounts here on the CT Shoreline and refreshing low maxes after all the heat and dry conditions this summer. Daily Precipitation Report Station Number: CT-FR-25 Station Name: Norwalk 2.9 NNW Data Explorer Observation Date 8/21/2025 7:00 AM Submitted 8/21/2025 6:38 AM Gauge Catch 1.75 in. Notes FallLike Day. 60s breezy. FINALLY RAIN!!! Started as mist late morning. Moderate in afternoon. Heavy at 11pm. Rained overnight. Misting at OBS Data for August 20, 2025 through August 20, 2025 Click column heading to sort ascending, click again to sort descending. GROTON NEW LONDON AP WBAN 1.58 NEW HAVEN TWEED AP WBAN 0.73 RECORD EVENT REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 221 AM EDT THU AUG 21 2025 ...RECORD DAILY LOW MAXIMUM TEMPERATURE SET AT BRIDGEPORT CT... THE HIGH TEMPERATURE WAS ONLY 70 DEGREES WEDNESDAY, AUGUST 20 AT BRIDGEPORT SIKORSKY AIRPORT. THIS TIES THE OLD RECORD LOW MAXIMUM OF 70 DEGREES, SET IN 1990. RECORDS FOR THE BRIDGEPORT CT AREA GO BACK TO 1948. ALL CLIMATE DATA ARE CONSIDERED PRELIMINARY UNTIL REVIEWED BY THE NATIONAL CENTERS FOR ENVIRONMENTAL INFORMATION (NCEI).

Another reason that the high temperatures in desert cities can be similar or cooler to the outlying areas is due to something called the urban cooling island. It’s another reason greening urban desert cities is so important. Since it can lead to a 2C cooling inversion during the day. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL066534 During the day, downtown areas appear to be cooler than the suburbs in six cities out of eight: Abu Dhabi, Kuwait City, Las Vegas, Phoenix, Biskra, and Bikaner, with values ranging from the −5.33°C in Abu Dhabi to the −0.06°C in Las Vegas during the summer. This effect can be partially explained considering that bare soils (prevalent in the suburbs) absorb more sunlight than urban surfaces due to their low reflectivity, hence leading to the relatively higher temperature of suburban areas [Georgescu et al., 2011]. This thermal gradient between the city center and suburbs can become even more pronounced when irrigated vegetation is present in the urban sites, resulting in heat advection, subsidence, and strong latent heat fluxes over the city. Also, the gradient can be modulated through the local wind regime and larger-scale atmospheric circulation alike, resulting in additional surface temperature variability across the diverse cities [Oke, 1987]. SUHI values referred to urban + vegetation sites are, in general, lower than the ones for the downtown sites, resulting in a further reduction of the temperature from few tenths of degrees to the −2.36°C in Phoenix at day in summer. It is, in fact, during the summer that the difference between urban and suburbs testing sites becomes wider: this phenomenon may be connected with intensive urban irrigation, eventually resulting in a sharp decoupling between vegetation and precipitation and to a lowering of the effects of heat stress on plants [Jenerette et al., 2013]. An exception is here represented by Bikaner, where from June to August, the southwestern monsoon carries sporadic spells of intense precipitation, which lower more easily the temperatures in bare and “permeable” suburban substrates than in “impervious” man-made surfaces [Kharol et al., 2013]. In agreement with previous results [Lazzarini et al., 2013; Lazzarini and Ghedira, 2014], Abu Dhabi displays the sharpest UCI effect, probably associated with the fact that it is located on an island [Frey et al., 2006; Wulfmeyer et al., 2014] and that the strong sea breeze regime triggered by monsoonal winds during the summer can induce a significant reduction of the atmospheric boundary layer depth, with a consequent mitigation of sensible heat fluxes along the coast [Eager et al., 2008]. In contrast, Riyadh and Doha do not show any inversion effect in the UHI, although the summer SUHIs have lower values than the winter ones on average. Again, this is consistent with previous results [Gamo, 1996; Alghamdi and Moore, 2014; Hashem and Balakrishnan, 2014; Sasidharan et al., 2009] and could be a consequence of the scarce vegetation coverage in these two cities (landscaping activities are limited) and urban design [Alghamdi and Moore, 2014]. During the night, however, the classical UHI phenomenon is restored: bare soil surfaces cool down faster than man-made and vegetated surfaces, resulting in strong positive SUHI values across all the cities of the ensemble. Therefore, HDCs are not immune from the UHI effect but rather oscillate between a diurnal UCI effect and a classic UHI at night. Since only two cities (Abu Dhabi and Kuwait City) out of the six displaying this diurnal UCI/nocturnal UHI alternation are close to a water body, breezes do not seem to have a dominant role in determining these common patterns, albeit additional local forcing on fluxes could arise from mild slopes and anabatic/katabatic flows [Yoshino, 1984; Rendón et al., 2014; Chemel et al., 2008; Sun et al., 2009; Brazel et al., 2010]. Nonetheless, proximity to the sea remains an important factor in reducing temperature ranges (see, e.g., the case of Abu Dhabi, Doha, and Kuwait City). In contrast, vegetation abundance and typology could be among the main causes of UCI. Transpiration patterns, in fact, largely depend on photosynthetic pathways: in C3 and C4 plants, for example, transpiration predominantly takes place during the day [see Caird et al., 2007, and references therein], while in Crassulacean acid metabolism (CAM) plants carbon uptake mainly occurs at night, under condition less conductive to water loss via transpiration [Bartlett, 2014]. Day/night ranges in the downtown sites appear smaller than the ones in the suburbs, while the ranges at the different sites tend to be amplified during the summer, with the exception of Bikaner, where again the precipitation events associated to the Indian summer monsoon could play an important role in modulating suburban LSTs. These features can be explained considering the lower heat capacity of suburban bare soils, allowing for quick variations of temperature. Owed to the decoupling with precipitation, the seasonal variability of NDVI within urban areas is extremely weak. However, during the summer, the elevated temperatures characterizing the HDCs can still trigger intense water stress in urban vegetation [Julien et al., 2011], leading to a summer reduction of the vegetation coverage in general, in contrast with what is generally observed in temperate regions. Following Zhou et al. [2013], Figure 2 shows the SUHI seasonal cycle evolution for day (Figure 2a) and night (Figure 2b). SUHI is calculated both as the difference in LST between urban + vegetation and the suburbs sites (green lines and symbols) and between downtown and the suburbs (in red). Observations are marked with light dots (grey for SUHI(Dt) and green for SUHI(U + V)), while monthly average values are indicated by black triangles (SUHI(U + V)) and filled circles (SUHI(Dt)), and the corresponding standard deviation of LST and SUHI is represented in the form of horizontal and vertical error bars. Thick continuous lines represent the SUHI(U + V) and SUHI(Dt) seasonal cycle after band-pass filtering of fine temporal scales up to 1 week with a Morlet wavelet of central frequency ω0=6 [Mallat, 2008]. The SUHI seasonal dynamics still displays clear diurnal UCI signature, and urban + vegetation sites show the highest potential for cooling in HDCs. However, the seasonal evolution of the SUHI strongly varies from city to city, pinpointing how not a single factor but rather the interplay between urban form, vegetation abundance, and local to regional climatic forcing are ultimately driving the thermal regimes of these cities. Also, the role of vegetation is not always univocal: in Biskra during the day, and in Phoenix at night, urban + vegetation sites appear to be warmer than their downtown counterparts. In both cases, the urban + vegetation test sites are located on a mild slope, facing north in the case of Biskra and southwest in the case of Phoenix. The topographic slope and the exposition to sunlight during the day could play a more prominent role than the sole vegetation coverage in these two cases. In Phoenix, for example, the urban + vegetation test site could be affected at night by a thermal belt effect [Yoshino, 1984], otherwise absent in the downtown site at the bottom of the valley, more likely subject to katabatic flows. It is also clear that in the presence of extended urban vegetated areas, plants phenology, irrigation systems, and specific microclimatic conditions can all contribute to the evolution of the SUHI. We performed a comparative analysis of the SUHI effect of cities located in hot desert environments (HDCs) using satellite data processing techniques. The main aim was to identify common patterns in the thermal regime of HDCs, testing at the same time the occurrence of the UCI effect observed in single studies dedicated to arid land cities. During the day, an average SUHI inversion of around 2°C was confirmed in six cities from a pool of eight. This inversion has been often associated with the abundance of irrigated vegetation in HDCs, which creates large areas where surface temperatures are mitigated through evaporative cooling. Despite that, the night LST analysis showed the standard UHI effect in all the cities. During the year, the variation of LST mainly showed a biseasonal mode, with a more evident inversion of SUHI during summer months. A comparative analysis of how the percentage of NDVI/ISA relates to LSTs also highlighted how medium dense urban sites with dedicated green areas are the ones showing the highest SUHI inversion probably due to the combined effect of shadowing and plant transpiration. However, all the cities displayed peculiar characteristics, pointing out how specific microclimatic and aridity conditions need to be taken into account in the SUHI assessment. Surface energy balance can be retrieved, and further variables (i.e., surface roughness and wind data) can be added to the picture, in order to better understand the microclimate of cities located in hyperarid regions. Seasonality of vegetation is expected to have a marginal role in HDCs due to the decoupling of vegetation from precipitation through irrigation [Jenerette et al., 2013]. In contrast, the typology of vegetation (C3, C4, or CAM) used in the landscaping could play a crucial role in mitigating (or reversing) UHI effects in desert cities. Also, the role of different irrigation strategies, as well as the link with desalination and its potential long-term impacts, needs to be addressed.

The summer JJA UHI effect in the Arizona South Central climate division is really pronounced for low temperatures at the Phoenix Sky Harbor International Airport. But the high temperatures there are fairly similar to the surrounding stations. The data below tracks the warmest Phoenix summers during the 1980s, 2000s, and 2020s. Unfortunately, several stations have left the network and new ones have joined. So several outlying stations don’t have a continuous record since 1981. This makes it difficult for a precise measurement of the UHI change since 1981. The one common denominator has been a steady rise in both the low and high temperatures for Arizona stations with a long enough period of record for comparison. AVG Max Temp Data for June 1, 2024 through August 31, 2024 Warmest Summer On Record Click column heading to sort ascending, click again to sort descending. PHOENIX AIRPORT WBAN 110.4 BUCKEYE 5N COOP 110.2 YOUNGTOWN COOP 110.0 GILA BEND 2SE COOP 109.9 ROBSON RANCH COOP 109.8 TEMPE ASU COOP 109.4 EAST MESA COOP 108.9 BARTLETT DAM COOP 108.6 CASA GRANDE COOP 108.3 CASA GRANDE NATL MONUMENT COOP 108.0 APACHE JUNCTION 5 NE COOP 107.6 MORMON FLAT COOP 107.0 MESA FALCON FIELD WBAN 106.8 SCOTTSDALE MUNICIPAL AP WBAN 106.8 CASA GRANDE MUNICIPAL AP WBAN 106.5 PHOENIX DEER VALLEY MUNICIPAL AP WBAN 106.4 STEWART MOUNTAIN DAM COOP 106.1 FOUNTAIN HILLS COOP 106.0 PICACHO 8 SE COOP 105.8 CAREFREE COOP 105.6 BOYCE THOMPSON ARBORETUM COOP 104.0 PINNACLE PEAK COOP 102.0 AVG Min Temp Data for June 1, 2024 through August 31, 2024 Click column heading to sort ascending, click again to sort descending. PHOENIX AIRPORT WBAN 87.5 MESA FALCON FIELD WBAN 84.3 SCOTTSDALE MUNICIPAL AP WBAN 84.1 YOUNGTOWN COOP 83.3 PHOENIX DEER VALLEY MUNICIPAL AP WBAN 82.0 MORMON FLAT COOP 81.6 GILA BEND 2SE COOP 81.5 EAST MESA COOP 81.4 BUCKEYE 5N COOP 81.3 FOUNTAIN HILLS COOP 80.2 CASA GRANDE MUNICIPAL AP WBAN 79.7 APACHE JUNCTION 5 NE COOP 78.9 PICACHO 8 SE COOP 78.9 CASA GRANDE COOP 78.7 PINNACLE PEAK COOP 78.5 CAREFREE COOP 77.7 TEMPE ASU COOP 77.6 BOYCE THOMPSON ARBORETUM COOP 77.6 CASA GRANDE NATL MONUMENT COOP 76.8 ROBSON RANCH COOP 76.2 AVG Max Temp Data for June 1, 2007 through August 31, 2007 Warmest Summer 2000s Click column heading to sort ascending, click again to sort descending. GILA BEND 2SE COOP 108.2 LAVEEN 3 SSE COOP 108.1 MARICOPA 4 N COOP 107.5 TONOPAH COOP 107.2 BARTLETT DAM COOP 107.0 PAINTED ROCK DAM COOP 106.7 CASA GRANDE COOP 106.3 PHOENIX AIRPORT WBAN 106.3 EAST MESA COOP 106.0 YOUNGTOWN COOP 105.5 TEMPE ASU COOP 105.2 ARIZONA CITY COOP 105.2 SACATON COOP 104.9 CASA GRANDE NATL MONUMENT COOP 104.7 STEWART MOUNTAIN DAM COOP 104.7 LITCHFIELD PARK COOP 104.4 PICACHO 8 SE COOP 104.1 FLORENCE COOP 104.0 APACHE JUNCTION 5 NE COOP 104.0 MORMON FLAT COOP 103.8 FOUNTAIN HILLS COOP 103.6 PHOENIX DEER VALLEY MUNICIPAL AP WBAN 103.6 SCOTTSDALE MUNICIPAL AP WBAN 103.5 CAREFREE COOP 102.9 WICKENBURG COOP 102.6 AGUILA COOP 102.3 WITTMANN 1SE COOP 102.0 AVG Min Temp Data for June 1, 2007 through August 31, 2007 Click column heading to sort ascending, click again to sort descending. PHOENIX AIRPORT WBAN 83.6 SCOTTSDALE MUNICIPAL AP WBAN 81.0 MORMON FLAT COOP 80.5 PHOENIX DEER VALLEY MUNICIPAL AP WBAN 80.0 YOUNGTOWN COOP 79.5 LITCHFIELD PARK COOP 79.3 GILA BEND 2SE COOP 78.7 PAINTED ROCK DAM COOP 77.9 FOUNTAIN HILLS COOP 77.8 EAST MESA COOP 77.0 PICACHO 8 SE COOP 76.7 PINNACLE PEAK COOP 76.4 MARICOPA 4 N COOP 76.0 CAREFREE COOP 76.0 FLORENCE COOP 75.9 TONOPAH COOP 75.6 STEWART MOUNTAIN DAM COOP 75.5 APACHE JUNCTION 5 NE COOP 75.1 TEMPE ASU COOP 75.1 CASA GRANDE NATL MONUMENT COOP 75.0 CASA GRANDE COOP 74.9 WITTMANN 1SE COOP 74.9 ARIZONA CITY COOP 74.3 SACATON COOP 74.2 BARTLETT DAM COOP 74.2 HORSE CAMP CANYON ARIZONA RAWS 71.1 WICKENBURG COOP 70.7 AVG Max Temp Data for June 1, 1981 through August 31, 1981 Click column heading to sort ascending, click again to sort descending. GILA BEND 2SE COOP 110.3 BUCKEYE COOP 109.9 LITCHFIELD PARK COOP 108.6 CASA GRANDE COOP 108.0 CASA GRANDE NATL MONUMENT COOP 107.9 SACATON COOP 107.6 TONOPAH COOP 107.2 PHOENIX CITY WBAN 106.9 MARICOPA 4 N COOP 106.9 FOUNTAIN HILLS COOP 106.8 YOUNGTOWN COOP 106.7 FLORENCE COOP 106.5 PHOENIX AIRPORT WBAN 106.1 MESA COOP 105.8 TEMPE COOP 105.7 CHANDLER HEIGHTS COOP 105.3 SCOTTSDALE COOP 105.1 BARTLETT DAM COOP 104.7 DEER VALLEY COOP 104.5 STEWART MOUNTAIN DAM COOP 103.8 ELOY 4 NE COOP 103.8 LAVEEN 3 SSE COOP 103.7 MORMON FLAT COOP 103.3 WICKENBURG COOP 103.2 SOUTH PHOENIX COOP 102.4 AGUILA COOP 101.6 AVG Min Temp Data for June 1, 1981 through August 31, 1981 Click column heading to sort ascending, click again to sort descending. PHOENIX AIRPORT WBAN 83.4 PHOENIX CITY WBAN 81.9 GILA BEND 2SE COOP 78.9 PHOENIX SOUTH MOUNTAIN COOP 78.9 LAVEEN 3 SSE COOP 78.1 FOUNTAIN HILLS COOP 77.5 YOUNGTOWN COOP 77.5 TONOPAH COOP 77.2 DEER VALLEY COOP 77.1 LITCHFIELD PARK COOP 76.9 MORMON FLAT COOP 76.6 STEWART MOUNTAIN DAM COOP 76.2 BARTLETT DAM COOP 75.8 MESA COOP 75.5 SUPERIOR COOP 75.1 MARICOPA 4 N COOP 75.0 BUCKEYE COOP 74.8 FLORENCE COOP 74.7 CHANDLER HEIGHTS COOP 74.6 TEMPE COOP 74.5 CASA GRANDE NATL MONUMENT COOP 74.3 ELOY 4 NE COOP 74.2 CASA GRANDE COOP 73.2 SOUTH PHOENIX COOP 73.1 AGUILA COOP 71.1 SCOTTSDALE COOP 70.3

Already a 7 foot swell before the 15+foot swell arrives tomorrow.

UHI acts as an amplifier of mostly the low temperatures in and around Phoenix leading to the rapid increase in 80° minimums there. But the rapid increase in 100°+ maxes is evenly distributed across, urban, suburban, and rural locations. It’s the rapid warming of the planet which is driving the increasing intensity of the heat. So the UHI acts to keep the urban centers warmer at night than the outlying areas. But both areas as seeing steep increases in the minimum and maximum temperatures. So without the background warming of the climate, the UHI alone wouldn’t be nearly as significant.

The faster Northern Stream of the Pacific Jet helped to suppress the weaker Southern Stream during the split flow intervals last winter. So it prevented those storms from coming further north. This has been the same theme since 2018-2019 with Great Lakes cutters, I-78 to I-84 huggers, and suppressed Southern Stream storm tracks.

The 2020s has produced unprecedented summer warmth for both locations. Flagstaff and Phoenix both had their warmest summers on record in 2024 by a significant margin. All the 2020s summers have been in the top 10 for warmth which has never happened before. Time Series Summary for Flagstaff Area, AZ (ThreadEx) 10 Warmest Summers dense rank sorting by temperature Click column heading to sort ascending, click again to sort descending. 1 2024 68.4 0 2 1981 66.6 0 3 2002 66.3 0 4 2025 66.2 13 5 2021 66.1 0 6 2020 65.8 0 - 2007 65.8 0 - 1974 65.8 0 - 1940 65.8 0 7 2018 65.6 0 8 2022 65.4 0 - 2008 65.4 0 - 1980 65.4 0 9 2012 65.3 0 - 1946 65.3 0 10 2023 65.2 0 - 2017 65.2 0 - 1996 65.2 0 - 1977 65.2 0 Time Series Summary for Phoenix Area, AZ (ThreadEx)10 Warmest Summers dense rank sorting by temperature Click column heading to sort ascending, click again to sort descending. 1 2024 98.9 0 2 2023 97.0 0 3 2025 96.7 13 - 2020 96.7 0 4 2015 95.1 0 - 2013 95.1 0 5 2019 94.9 0 - 2007 94.9 0 6 2011 94.8 0 - 2002 94.8 0 - 1981 94.8 0 7 2022 94.7 0 8 2017 94.6 0 - 2016 94.6 0 - 2003 94.6 0 9 2006 94.5 0 10 1989 94.4 0 - 1988 94.4 0

If you look at the JJA 20 year trend from 1995 to 2024, then the high/low trend is nearly identical for both stations. The minimums are rising at a faster pace for both locations. Obviously, Phoenix gets the most attention since the actual temperatures are significantly higher. But the temperature increase at both locations has been the same even at significantly different altitudes. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/city/time-series/USW00003103/tmin/3/8/1995-2024?trend=true&trend_base=10&begtrendyear=1995&endtrendyear=2025&filter=true&filterType=binomial 1995-2024 temperature trend Phoenix……max…+0.8°F/Decade….min…+1.0°F/Decade Flagstaff…..max…+0.7°F/Decade…min…..+.1.1°F/Decade

Yeah, nice to see the Euro start showing a PRE since we really need it. But the placement of these features can be very fickle like IVTs in the winter. We can remember back in 2021 showing the PRE in SNJ and it would up in NYC. But at least there is now the potential for someone around the area to get some much needed rainfall even if later runs switch the location near the jet entrance region.

The four major climate sites in Arizona on NOAA NCEI have all experienced a steep increase in summer temperatures since 1971. But the rate of increase at Phoenix for daily minimum temperatures is faster than the other sites.The increase in maximum temperatures across the four major climate sites has been fairly uniform. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/city/time-series/USW00003103/tmin/3/8/1971-2024?trend=true&trend_base=10&begtrendyear=1971&endtrendyear=2025&filter=true&filterType=binomial 1971-2025 Arizona increase in JJA temperatures Phoenix….min…+1.0°F/ Decade….max….+0.8°F/Decade Flagstaff…min….+0.9°F/Decade…max…..+0.5°F/Decade Tucson…..min….+0.6°F/Decade…max…..+0.8°F/Decade Yuma……..min….+0.7°F/Decade…max…..+0.8°F/Decade

Maybe the EPS shifting to a deeper trough and stronger cold front passage next Monday could actually give us some organized rainfall rather than the spotty convection of late leading to the developing dry pattern. New run Old run

Some records from 1993 have been very difficult to beat. It still remains the only year where the warm spots had 100° heat from June through September. Was the only year with 9 days getting to 100°. But the 2020s are getting close to surpassing the 1990s for total 100° days with 4 years to go. The 2020s only need 3 more 100° days to set the new record. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ June Through September Maximum Temperatures Click column heading to sort ascending, click again to sort descending. 2025 103 101 96 M 103 2021 103 97 99 91 103 2011 102 108 98 88 108 1994 102 99 95 92 102 1993 102 105 100 100 105 1952 102 98 92 94 102 1943 102 95 97 93 102 1988 101 101 99 86 101 1966 101 105 95 91 105 2024 100 99 100 87 100 1959 100 93 96 93 100 1953 100 99 102 105 105 1934 100 98 90 85 100 1923 100 99 92 90 100 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Jan through Dec 100° Days Click column heading to sort ascending, click again to sort descending. 1 1993 9 0 2 1949 8 0 3 2025 7 136 4 2022 6 0 - 1953 6 0 6 1988 5 0 - 1966 5 0 100° days 1990s….19 days 2020s…17 days 1940s….16 days 1950s….15 days 2010s….13 days 2000s…11 days 1980s….9 days 1960s….6 days 1970s….3 days

While the sample size is pretty small, there has been an increase in NYC La Niña snowfall following Atlantic hurricane seasons with 160+ ACE since 1995. There was also an increase in December +PNAs. Unfortunately, the relationship didn’t work last winter due to the overpowering Northern Stream of the Pacific Jet. Last season was the first with only 12.9” of snowfall in NYC with a strong December +PNA and a La Niña. My guess is that the high ACE was part of a similar pattern which used to produce both December +PNAs and snowy outcomes during La Nina’s. So while we got the strong December +PNA last season, the snowfall didn’t follow due to the warm storm track through the Great Lakes. So several elements in the same pattern but we can’t say that the ACE is directly the cause. Just that these elements appear together from time to time. It could be they are related to another underlying variable that we haven’t identified yet. 2005….ACE…..245….DEC PNA….+1.38….NYC snowfall….40.0” 1995….ACE……227….DEC PNA…..+0.92..NYC snowfall ….75.6” 2017….ACE……224….DEC PNA…..+0.89…NYC snowfall….40.9” 1998…ACE……181……DEC PNA…..-0.09….NYC snowfall…..12.7” 2020..ACE……180…..DEC PNA…..+1.58….NYC snowfall….38.6” 1999…ACE……176…..DEC PNA……+0.21….NYC snowfall…..16.3” 2010…ACE…..165……DEC PNA…….-1.78….NYC snowfall…..61.9” 2024…ACE….161……DEC PNA…….+1.70….NYC snowfall…..12.9”

We can look at the SST data for the WPAC over the last 10 years and see that this has been a top down rather than bottom up warming process. The subsurface charts show warming starting at the surface around 10 years ago and gradually working down. It also matches the increase in high pressure and drop in clouds. This is consistent with the warming we have seen in other oceans like the Atlantic following light winds, more sunshine, higher pressure, and fewer clouds.

Looks like we get a break for a while on the mid 90s after today. This week should be very close to seasonable for the temperarures. But unfortunately it still looks drier than normal. August 18-25 forecast