Phoenix Experiences Its Hottest Summer on Record for the Third Time in Five Years

[Typhoon Tip]

44 minutes ago, donsutherland1 said:

The heat so far in October has been made at least 5 times as likely by climate change in the Phoenix area and a large swath of the southwestern United States.

i like how the bay area of san francisco got whacked by 90+ heat.  it's very hard to do that there.   that w--> e replacement flow through the golden gate straight is very difficult to stop and takes some pretty amazing circumstances to stop it.   i've been out there when it was 101 on the eastern shore of the bay and we couldn't get over 70 down by the marina district.  on the other side of the penn on the pac side it's in the 60s with pants flapping in the crushing onshore laminar flow.  yet i think they've been close to 80 on the sand in this thing

[donsutherland1]

1 hour ago, Typhoon Tip said:

i like how the bay area of san francisco got whacked by 90+ heat.  it's very hard to do that there.   that w--> e replacement flow through the golden gate straight is very difficult to stop and takes some pretty amazing circumstances to stop it.   i've been out there when it was 101 on the eastern shore of the bay and we couldn't get over 70 down by the marina district.  on the other side of the penn on the pac side it's in the 60s with pants flapping in the crushing onshore laminar flow.  yet i think they've been close to 80 on the sand in this thing

The 95-degree high in SF was really impressive.

[donsutherland1]

October 1-7, 2024 saw Phoenix demolish the record for its hottest first week of October on record. No prior October heatwave even begins to compare. Even a synthetic heatwave constructed of all October 1-7 pre-2024 record high maximum and minimum temperatures was smashed.

Climate change played a leading role in driving the unprecedented heat, which included a 14-consecutive day stretch of record tying and record breaking high temperatures (September 24-October 7). According to Climate Central's Climate Shift Index, the heat in Phoenix and surrounding areas (including rural areas not impacted by the Urban Heat Island Effect) was made at least five times as likely due to climate change.

Select Charts:

The October 1-7, 2024 96.1° 7-day mean temperature was so extreme that it falls outside of what would statistically be expected using a 99.9% confidence interval based on 30-year moving average October 1-7 mean temperatures.

The incredible late-season heat was widespread in the Southwest. Numerous records were broken, some by very large margins.

[donsutherland1]

Here is how Arizona's record book was rewritten during the 14-day September 24-October 7, 2024 period:

[TheClimateChanger]

15 consecutive days of record heat. Unreal.

 

[TheClimateChanger]

4 minutes ago, TheClimateChanger said:

15 consecutive days of record heat. Unreal.

 

Per ThreadEx, 63 of 365 days in 2023 saw high temperatures among the three warmest of record, and 60 of 365 days in 2023 saw low temperatures among the three warmest of record. 2024 data is not available, but it probably is even crazier.

[TheClimateChanger]

12 minutes ago, TheClimateChanger said:

15 consecutive days of record heat. Unreal.

 

Also, I don't believe for a minute the temperatures reported for Burlington, Iowa in 1936. It was hot, but it's clear there was a massive warm bias at wherever the records were taken. As an apparent co-op site, it likely also suffered from a TOBs bias.

Compare it to Moline. At the current sites, it averages about 1F cooler in the month of July. But in July 1936, it was more than 3F warmer.

Moline

Burlington

[TheClimateChanger]

The record-breaking heat wave at Phoenix has now reached 16 days. Record for today is 105F, and the current forecast for PHX airport is 106F. So decent odds we add a 17th consecutive record high today.

[TheClimateChanger]

2 minutes ago, TheClimateChanger said:

The record-breaking heat wave at Phoenix has now reached 16 days. Record for today is 105F, and the current forecast for PHX airport is 106F. So decent odds we add a 17th consecutive record high today.

In fact, the current forecast has record high temperatures continuing through Columbus Day, which would bring the streak up to 21 consecutive record-breaking or record-tying high temperatures. Three consecutive weeks of record highs. Insane.

[donsutherland1]

3 hours ago, TheClimateChanger said:

In fact, the current forecast has record high temperatures continuing through Columbus Day, which would bring the streak up to 21 consecutive record-breaking or record-tying high temperatures. Three consecutive weeks of record highs. Insane.

The United States and probably all of North America has never seen anything like this autumn heatwave. The combination of extreme warmth and persistence is almost uncertainly unmatched. "Unprecedented" doesn't adequately describe what has occurred. During this heatwave, the September monthly record of 117° on 9/28, the October record of 113° (10/1, 10/6), and 10/1-7 mean temperature of 96.1° at Phoenix were all beyond 1000-year events (less than 0.1% chance of occurring in any year). All of this happened during the same heatwave.

 

[TheClimateChanger]

19 hours ago, donsutherland1 said:

The United States and probably all of North America has never seen anything like this autumn heatwave. The combination of extreme warmth and persistence is almost uncertainly unmatched. "Unprecedented" doesn't adequately describe what has occurred. During this heatwave, the September monthly record of 117° on 9/28, the October record of 113° (10/1, 10/6), and 10/1-7 mean temperature of 96.1° at Phoenix were all beyond 1000-year events (less than 0.1% chance of occurring in any year). All of this happened during the same heatwave.

 

I know Hawaii - especially Honolulu and Kahului - had a lot of record highs in 2019. Kahului had 20 of 23 days with record highs [some have since fallen]. You'd think something like this - if it were to occur - would be in a place with very low variation, where globally warmed ocean surface temperatures could push the highs up 2-3F to record levels day after day. Places like Hawaii or Key West. You wouldn't expect it in the continental interior, where there's tons of variability. And I know it's a little less in Arizona, but still... no late season monsoonal push of moisture to disrupt the trend, no push of modified Pacific air, no cold front from the interior.

And it's more impressive from a departure standpoint. In a maritime climate, those record highs might only be 5F above the normal high temperatures. Phoenix has had day after day of 15F+ departures from normals that have already risen substantially from prior decades.

[donsutherland1]

6 hours ago, TheClimateChanger said:

I know Hawaii - especially Honolulu and Kahului - had a lot of record highs in 2019. Kahului had 20 of 23 days with record highs [some have since fallen]. You'd think something like this - if it were to occur - would be in a place with very low variation, where globally warmed ocean surface temperatures could push the highs up 2-3F to record levels day after day. Places like Hawaii or Key West. You wouldn't expect it in the continental interior, where there's tons of variability. And I know it's a little less in Arizona, but still... no late season monsoonal push of moisture to disrupt the trend, no push of modified Pacific air, no cold front from the interior.

And it's more impressive from a departure standpoint. In a maritime climate, those record highs might only be 5F above the normal high temperatures. Phoenix has had day after day of 15F+ departures from normals that have already risen substantially from prior decades.

Yes. San Juan has seen its hottest May, June, July, August, and September on record this year due, in large part, to an ongoing marine heatwave. It has also seen 115 record high minimum temperatures (tied or new records) this year.

Phoenix's extreme heat is a result of the persistence of an exceptional heat dome regime (made more likely by climate change). Today is now its 18th consecutive record-tying or record-breaking high temperatures. A dramatic pattern change thanks to the powerful storm now battering Alaska should finally break the heat. It remains to be seen whether the heat will try to return yet again late this month or during November, even as temperatures will be well below the recent extremes.

[Typhoon Tip]

while not at the scale of precedence discussed in this thread to date ... the warm up spanning the n ov to ne and n ma region from late friday thru early this next week has some potential to be historic.

we've been monitoring a robust +500 mb anomaly in both the individual operation versions, all of which is very well statistically anchored by the teleconnector modes/modalities during the period. 

the particulars/dailies have the ambient polar boundary anomalously situated n of seasonality, with a very large circumvallate of 850 mb temperatures above +12c through said region, under the influence of dvm/associated higher surface pressure.  well established deep layer west wind transports w ejected mass spanning a minimum of 3 days - may only be 2 day but given to what is also non-deviated continuity for this signal in the above spectrum of guidance., it may take us into early next week. 

the sun is feeble(r) - that is apparently the only limiting factor.  can it dump enough energy into the described environment to max the potential.  probably not I'd say...but given to 80 or so % of what that is, would still make these records below vulnerable.  note, in 2020 we achieved 79 to 83 at sites in the interior of sne as late as november 9.  

i was looking around at records for oct 18 and 19.  hartford ct     part of this is a bit experimental. we are observing 'over achieving' warmth just about whenever a pattern is conducive to positive anomalies, world over... relative to climo and/or predictive methods ( machine and experience or both).   this look in the 500 mb/ 850 thermal layout/ synoptic tapestry is a 'smoking gun' for testing that again...

October 18	84	2016
October 19	82	1963

October 20

81

1969

both new york and boston are similar

[donsutherland1]

Phoenix saw the temperature soar to 103° on October 14th. That smashed the daily record of 100° that was set in 1973 and tied in 2010, 2015, and 2020. It also concluded a record-obliterating 21-day stretch during which Phoenix tied or broke its daily record high temperatures. The previous U.S. record was 14 consecutive days at Burlington, IA during July 4-17, 1936. That Phoenix has a climate record that goes back to August 1895 makes such a streak particularly mind-boggling. There has never been an autumn heatwave like the one that rewrote a significant portion of Phoenix's autumn record book.

The average temperature during the streak was 94.8°. The average high was 109.0° and the average low was 80.7°. Phoenix's average low temperature and mean temperature during this period set new Arizona state records. Phoenix's mean temperature also set a national record for the period.

The average daily high temperature broke the daily record by an average of 3.8°. On September 28th, the 117° high temperature set a new September monthly record, tied the August monthly record, and demolished the prior daily mark by 9°. Prior to 2024, the October monthly record was 107°. That record was surpassed on eight consecutive days (October 1-8), with four readings reaching or exceeding 110°.

 

 

[TheClimateChanger]

For the visual folks:

What I find most startling here is the record before 2020 was 33 days [and even those were fairly recent]. Three of the last 5 summers have beaten the pre-2020 record by 20 or more days!

"We do a lot of firsts. Let me tell you folks, we do a lot of firsts." - Donald J. Trump

[bdgwx]

This brings Phoenix's count of daily high records (including both minimum and maximum) to 72 so far in 2024.

However, this pales in comparison to San Juan which has reported 141 record highs (including both minimum and maximum) so far in 2024.

[donsutherland1]

9 hours ago, bdgwx said:

This brings Phoenix's count of daily high records (including both minimum and maximum) to 72 so far in 2024.

However, this pales in comparison to San Juan which has reported 141 record highs (including both minimum and maximum) so far in 2024.

Thanks to unrelenting marine heatwaves, San Juan has had 120 80° or above low temperatures this year. Last year, which set the prior record, the mark was 89 days. Before 2023, the record stood at 59 days (2009). So, the record has been more than doubled in just two years.

[donsutherland1]

With Phoenix's unprecedented autumn heatwave now in the books, some are trying to rewrite what happened in order to minimize the nature and magnitude of what took place.

The above post might seem informative. It isn't. It is an attempt to essentially erase the record-breaking nature of the heat. Phoenix broke its October high temperature record by 7°. That old record was set in 1980 and tied in 2020.  Subtract 10°, and suddenly the 2024 heatwave loses its record-breaking outcome.

Now for some facts:

1. Urban Heat Island (UHI) Effect is real. However, its largest impact is at night.

2. An attribution study that covered Phoenix during June-July 2023 (when the City saw a record 31 consecutive 110° days) found that the heat was "virtually impossible" without climate change and that climate change had made the heat 2°C (3.6°F) hotter. Using the attribution study for guidance, that means that 3.6° of the 6° margin by which Phoenix beat the 1980/2020 record or 60% was due to climate change. If one attributed all the rest of the margin to UHI, 40% was due to UHI.

3. If Maue's argument had validity, small locations not subject to UHI would not have set monthly records. In fact, they did. Ajo (Population: 2,922) broke its October record by 4°. Picacho (Population: 289) broke its monthly record by 5°.  Tacna (Population: 3,393) broke its October record by 3°. The average margin of record for these three sites that experience no UHI was 4°. Those numbers, which were due completely to climate change, are reasonably in line with the findings of the 2023 attribution study's 3.6° figure.

4. If one looks at the bigger picture, dozens of locations in Arizona and California smashed their October monthly records during the heatwave.

In sum, UHI amplifies heat. UHI made Phoenix hotter than it would otherwise have been, but the exceptional heat was not solely or largely an artifact of UHI. The heat was driven by climate change (otherwise small population areas would not have been smashing monthly records). Even without UHI, based on the attribution study and experience of small population sites, Phoenix would have set a new October record (probably topping out at 110°-111° vs. 113°). The heat would still have been unprecedented for the season, both for its magnitude and its persistence.

 

[TheClimateChanger]

2 hours ago, donsutherland1 said:

With Phoenix's unprecedented autumn heatwave now in the books, some are trying to rewrite what happened in order to minimize the nature and magnitude of what took place.

The above post might seem informative. It isn't. It is an attempt to essentially erase the record-breaking nature of the heat. Phoenix broke its October high temperature record by 7°. That old record was set in 1980 and tied in 2020.  Subtract 10°, and suddenly the 2024 heatwave loses its record-breaking outcome.

Now for some facts:

1. Urban Heat Island (UHI) Effect is real. However, its largest impact is at night.

2. An attribution study that covered Phoenix during June-July 2023 (when the City saw a record 31 consecutive 110° days) found that the heat was "virtually impossible" without climate change and that climate change had made the heat 2°C (3.6°F) hotter. Using the attribution study for guidance, that means that 3.6° of the 6° margin by which Phoenix beat the 1980/2020 record or 60% was due to climate change. If one attributed all the rest of the margin to UHI, 40% was due to UHI.

3. If Maue's argument had validity, small locations not subject to UHI would not have set monthly records. In fact, they did. Ajo (Population: 2,922) broke its October record by 4°. Picacho (Population: 289) broke its monthly record by 5°.  Tacna (Population: 3,393) broke its October record by 3°. The average margin of record for these three sites that experience no UHI was 4°. Those numbers, which were due completely to climate change, are reasonably in line with the findings of the 2023 attribution study's 3.6° figure.

4. If one looks at the bigger picture, dozens of locations in Arizona and California smashed their October monthly records during the heatwave.

In sum, UHI amplifies heat. UHI made Phoenix hotter than it would otherwise have been, but the exceptional heat was not solely or largely an artifact of UHI. The heat was driven by climate change (otherwise small population areas would not have been smashing monthly records). Even without UHI, based on the attribution study and experience of small population sites, Phoenix would have set a new October record (probably topping out at 110°-111° vs. 113°). The heat would still have been unprecedented for the season, both for its magnitude and its persistence.

 

@donsutherland1 - it is curious how this "urban heat island" effect suddenly appeared in Phoenix after 2019, which I pointed out is when 3 of 5 years saw 20+ days more of 110+ afternoons than any prior year. I wonder how the proponents of this "urban heat island" theory rectify their theory with the actual data? Surely, Phoenix has been a very large American city for decades at this point. Why was something like this never observed before 2020? Almost like there's something else going on here.

[TheClimateChanger]

Here is the historical population data for Phoenix. Weird how this "urban heat island" effect wasn't a big deal in 2000, when the population was more than 1.3 million, or 1990, when the population was about 1 million, or 1980, when the population was about 800,000. It just suddenly appeared in 2020, when heat records were being broken left and right. Fascinating phenomena.

[TheClimateChanger]

If we look at the 10 hottest years at Phoenix, we see a number of recent years with means ranging from 76.4F to 77.3F. I suspect 2024 will eclipse these, but the year is not yet complete.

But if we subtract Maue's speculated 10F urban heat island effect, then we see all of these years were actually far cooler than the coldest years on record. Astounding!

What we can conclude then is rural areas have warmed considerably, but Phoenix [and only Phoenix] has actually cooled considerably but the urban heat island has corrupted the data to such an extent that it looks like it has warmed. Fascinating theory.

[donsutherland1]

32 minutes ago, TheClimateChanger said:

@donsutherland1 - it is curious how this "urban heat island" effect suddenly appeared in Phoenix after 2019, which I pointed out is when 3 of 5 years saw 20+ days more of 110+ afternoons than any prior year. I wonder how the proponents of this "urban heat island" theory rectify their theory with the actual data? Surely, Phoenix has been a very large American city for decades at this point. Why was something like this never observed before 2020? Almost like there's something else going on here.

I agree. The growing coverage of extraordinary heat--in this case, an unprecedented autumn heatwave with nothing comparable in the U.S. climate record--has made it very difficult for those who dismiss or deny AGW to do so with any degree of credibility. Therefore, they desperately invoke issues that seem realistic. But when the data is examined more closely, their bad arguments disintegrate.

[donsutherland1]

Phoenix's fall temperatures (10-year moving average) have been increasing relative to climate model projections (RCP 4.5), but have been running consistently above the 75th percentile for model projections.

[donsutherland1]

Phoenix and Tucson are poised to see yet another round of record-challenging and record-breaking heat starting tomorrow. Phoenix could see one of its latest 100° temperatures on record. Tucson could see its latest 100° temperature on record.

[TheClimateChanger]

On 10/22/2024 at 5:08 PM, donsutherland1 said:

Phoenix and Tucson are poised to see yet another round of record-challenging and record-breaking heat starting tomorrow. Phoenix could see one of its latest 100° temperatures on record. Tucson could see its latest 100° temperature on record.

The 100F record high for 10/27, set in 2016 is the latest 100F+ on record at Phoenix, so that's certainly well within reach.

[lookingnorth]

It looks like Tucson didn't hit 100, but they still managed to set 3 daily records, topping out at 99.

[Typhoon Tip]

I think that 95+ in oklahoma was staggering.  it broke previous records by like 5 to 7 deg

[donsutherland1]

Phoenix remains on course to see its warmest October on record. Looking back at the summer, the U.S. Southwest has been experiencing hotter summers, both in terms of minimum and maximum temperatures. The increased heat has been translating into extreme temperatures (upper 10% of the climate record). The regional figures (percentage of area experiencing extreme temperatures) include all areas, not just urban areas. That a growing share of the region is experiencing extreme readings demonstrates that UHI is not driving the warmth; it is amplifying the warmth in cities such as Phoenix, but the entire region, including rural areas, is warming.

Maximum Temperatures: Percentage of Region with Average Maximum Temperatures in the Highest/Lowest 10th percentile:

Minimum Temperatures: Percentage of Region with Average Minimum Temperatures in the Highest/Lowest 10th percentile:

The data also suggests that a long-term process of aridification may be in its early stages. Regional aridification is predicted by the climate models. More data will be required for a more definitive conclusion on that issue. The data shows that the percentage of the region experiencing severe drought (lowest 10th percentile) based on the Palmer Drought Severity Index (PDSI) has also been increasing in recent years.

 

 

[donsutherland1]

Powered by an unprecedented record-melting autumn heatwave that was unlike anything in the Southwest’s climate record, Phoenix experienced its warmest October on record. “Unprecedented” seems almost inadequate to describe the heatwave that stretched from the last week of September through the first week of October.

During the first eight days of October, Phoenix eclipsed the previous monthly record high temperature on eight consecutive days. It also set a new monthly record high minimum temperature on two consecutive days.

Climate change has played a large role. The 25th and 75th percentiles climate model projections (RCP 4.5) for fall were 72.9°-75.1° during 1961-1990 and 74.5°-76.7° for 1991-2020. The actual outcomes were 73.8° and 77.1°, respectively. The climate model projections for 2001-2030 are 75.1°-77.5°. The projections for 2011-2040 are 75.7°-78.2°.

[donsutherland1]

Phoenix Follows its Hottest Summer with its Warmest Fall on Record

Phoenix experienced its warmest fall on record. An unprecedented autumn heatwave that was unlike anything in the Southwest’s climate record drove the outcome. Phoenix finished with a seasonal mean temperature of 81.1° (1^st highest), seasonal average high temperature of 93.7° (1^st highest), and seasonal average low temperature of 68.5° (2^nd highest).

Climate change has played a leading role. Since 1895, there were 14 fall cases with a seasonal mean high temperature of 90° or above. The first occurred in 1933. Since 2000, there were 9 such cases (64% of cases) even as the 2000-2024 period comprised 19% of Phoenix’s climate record. Since 2010, there were 6 such cases (43% of cases) even as the 2010-2024 period made up 12% of Phoenix’s climate record. Since 2020, there have been 4 such cases (29% of cases), even as the 2020-2024 period accounted for 4% of Phoenix’s climate record. On account of the long, warm fall, Phoenix’s year-to-date average temperature finished November at 80.1°. The previous record latest 80° or above year-to-date average temperature was November 12, 2020. The previous highest year-to-date temperature through November 30^th was 79.3° in 2020.

On account of the record hot summer and record warm Fall, Phoenix is virtually certain to experience its warmest year on record. Prior to the start of summer, 2024 was tied for the 21^st warmest year on record, 2.2° below the mean for 2014, which was the warmest year on record through May 31^st.