ChescoWx

Of note the 41.1 degree low this morning in East Nantmeal is the coolest reading this early in Chester County in 30 years since the 41 degree low on September 17, 1990

Record AM low today of 41.1 breaking the old mark of 42.0 set back in 1990. The all-time lower elevation record low is 36.0 set back in 1929 and 1943

A new record low max for September 15th here in Western Chester County PA with a high of only 62.7 today. All-time mark of of 58.0 from 1963 still in tact. Today's double digit negative departure - 1st since May 12th. Likely we will have a below normal month through at least the 21st of the month

Summer (June thru August) climate summary for Western Chester County PA. For the summer months (Jun-Jul-Aug) here in Western Chester County we finished with an average temperature of 73.7 This is the 17th warmest summer since 1894 Of note the 5 hottest summers were all before 1955 (warmest being the summer of 1900 at 75.8 degrees!) Coldest reading - 44.1 on June 1st Warmest reading - 92.0 on July 19th Only our 2nd heat wave (3 straight 90+ days) in the last 8 years!! We have had only 10 heat waves in the last 18 years 5 days exceeded 90 degrees this summer - our most in 9 years since the 11 back in 2011 Of interest only 4 of the 17 warmest summers have occurred since 1988 and the top 5 all before 1956 and 13 of the 17 warmest summers also occurred prior to 1956 Top 5 warmest summers were (1900 - 75.8 / 1901 - 75.0 / 1944- 75.0/ 1955 - 75.0 and 1943 -74.9) Precipitation wise we received 17.63" of rain - average summer months rainfall is 13.16" (+4.49" above avg.) This was the 15th wettest summer on record with the wettest occurring just 2 summers ago in 2018 when 26.29" of rain drenched Western Chesco Finally an fascinating comparison (see attached) that helps highlight the increasing heat island impact at the Philadelphia Airport compared to the more rural observation suburban burbs in Eastern PA where we are noting a decline in 90+ days. In just the last 2 years PHL airport has recording 67 days above 90 degrees (the other 3 sites combined over the last 4 years only 61 days!) With 17 years of records for these locations - Note that over the last 8 years a significant drop in the number of 90+ days at the rural sites compared to the prior 9 years However at the Philadelphia airport - the frequency of 90+ days continues to increase at a fast pace....this disparity is likely to continue as the heat island impact shows little sign of abating

.04" of rain since midnight and 0.14" storm total so far

AM Low today 66.5

Today's AM Low 61.2

Low this AM was 55.8 - lowest since the 52.7 on June 16th (think we need to add Phillies and Flyers Playoff pushes to the sub title of this thread)

August and Summer climate summary for Western Chester County PA. With an average temperature of 73.5 August 2020 finished at 1.3 degrees above normal (43rd warmest August on record) 8.36" of rain was 3.99" above normal - this was the 15th wettest August since records began in 1894 For the summer months (Jun-Jul-Aug) here in Western Chester County we finished with an average temperature of 73.7 This is the 17th warmest summer since 1894 Of interest only 4 of the 17 warmest summers have occurred since 1988 and the top 5 all before 1956 Top 5 warmest summers were (1900 - 75.8 / 1901 - 75.0 / 1944- 75.0/ 1955 - 75.0 and 1943 -74.9)

Indeed....why we need to be careful with what is truly warming based on what we now deem "official" sites....hence my analysis

Not that any one location either supports or refutes climate change (IMO... of course climate it is always changing - but it's just cyclical) However, If summer (June-July-Aug) ended today here in the leafy Western burbs of Philadelphia (35 miles west of PHL airport) our current summer average temperature of 73.8 degrees would represent our warmest summer in the philly burbs outside of the PHL Airport heat island since 2002 and 16th warmest since records began here in Chester County in 1894. I use the NWS Coop data set and my data which represents continuous daily data since January 1st , 1894. Of note there is some relative elevation differences that may account for some of the differences with Chester County data being observed at over 650ft ASL while PHL Airport lies near sea level on the Delaware River. The top 2 hottest summers? way back in 1900 & 1901. I also did some data analysis (see below) comparing the average suburban temperatures by decade outside of the PHL airport heat island impact to the official PHL readings. I only had PHL decade data for the last 70 years (7 decades) As you can see there has not been much warming in fact a clear warmer cycle in the early part of the 20th century followed starting with the 1940's with 4 straight decades with declining temps and now the last 4 decades starting with the 1980's showing warming....but nowhere near like the PHL heat island is indicating - in fact the 1990's were exactly the same as the 1st decade of the 20th century. While the 2010's were the warmest decade it was only by 0.3 degrees. It is interesting to note the much sharper and consistent rise at the PHL airport.