ChescoWx

Below is the average summertime (June thru August) average temperatures by decade for Chester County since the 1890's. The hottest complete decades were back in the 1930's and 1940's. We are only 3 years in to the 2020's but so far we are tied for 2nd warmest decade but plenty of years left to work on this decade.

Here in East Nantmeal we exceeded 90 degrees for just the 2nd time this year (90.5) with the 2nd hottest day of the year behind only the 91.9 on June 22nd. Other area high temps yesterday included Brandwine Airport (95.0) Chester Springs (94.9 ) and Warwick Twp. (94.0). Today will be even hotter with widespread mid to upper 90's. Shower chances increase later today and again tomorrow as a cold front moves through later Wednesday. It will turn much more comfortable by Thursday with temperatures closer to average for what is normally our warmest week of the year. Chester County Records for today: High 100 degrees at Coatesville (1900) / Low 46 degrees also at Coatesville (1929) / Rain 2.66" at Kennett Square (1911)

Here in East Nantmeal we exceeded 90 degrees for just the 2nd time this year (90.5) with the 2nd hottest day of the year behind only the 91.9 on June 22nd. Other area high temps yesterday included Brandwine Airport (95.0) Chester Springs (94.9 ) and Warwick Twp. (94.0). Today will be even hotter with widespread mid to upper 90's. Shower chances increase later today and again tomorrow as a cold front moves through later Wednesday. It will turn much more comfortable by Thursday with temperatures closer to average for what is normally our warmest week of the year. Chester County Records for today: High 100 degrees at Coatesville (1900) / Low 46 degrees also at Coatesville (1929) / Rain 2.66" at Kennett Square (1911)

Most spots except the higher elevations hit 90 degrees yesterday more of the same today and then even hotter Monday and Tuesday with mid to upper 90's especially in lower spots. Cold front slices thru by Wednesday night with temps close to normal but most importantly lower humidity by late week. Chester County records for today: High 102 degrees in Phoenixville (1954) / Low 50 degrees at Devault (1960)/ Rain 4.00" at West Grove (1975)

Most spots except the higher elevations hit 90 degrees yesterday more of the same today and then even hotter Monday and Tuesday with mid to upper 90's especially in lower spots. Cold front slices thru by Wednesday night with temps close to normal but most importantly lower humidity by late week. Chester County records for today: High 102 degrees in Phoenixville (1954) / Low 50 degrees at Devault (1960)/ Rain 4.00" at West Grove (1975)

The West Chester Data set has a ton of gaps or corrupted data (see raw data below) on the NCEI Bias calculations. It appears that about 32% of the years from 1893 to 2017 are impacted.

Hey Charlie...of note when reviewing the Coatesville 2W data from 1983 to 2007. There seems to be no adjustments between raw and adjusted etc. for any years....but the raw numbers unlike the Coatesville 1 SW data seems to be off almost every month and generally warmer than the actual observations. One example is January 1985. The below is the observations and this matches the data set I have been using. This averages out to a 24.2 average temperature for the month but the NCEI data lists the raw average for the month as 25.0. Any thoughts??

Hey guys thanks to Charlie (Chubbs) I was just able to figure out how to find detailed NCEI adjustments for individual stations in Chester County. I am starting with the original Coatesville 1SW station . Below is an analysis of the actual/raw average annual temperature data vs. the NCEI altered data for Coatesville 1SW from 1894 thru 1982. As discussed before NCEI has multiple reasons stated to support these adjustments. (Time of observation/ station moves/ equipment or siting issues etc.) But of interest the chilling adjustments were consistently applied to the first 71 years (1894 thru 1971) The greatest chilling adjustments were applied to the oldest data with at least 2 degrees F adjustments made from 1897 thru 1922 along with 1931-35 and 1941-45. The end result with the altered data (red) flips what the raw data (blue) clearly shows as cooling trend during those years....to now a clear warming trend. The greatest overall chilling adjustments were made to the October thru December months. But 100% of all months for all years were chilled for April through October. February had the least number of months chilled with 75 of the 89 months while January and March both saw chilling adjustments to 78 of the 89 months on record.

Below is the impact of the altered data for Coatesville 1SW from 1894 thru 1982. The chilling adjustments were consistently applied to the first 71 years (1894 thru 1971) The greatest chilling adjustments were applied to the oldest data with at least 2 degrees F adjustments made from 1897 thru 1922 along with 1931-35 and 1941-45. The end result with the altered data flips what the raw data clearly shows as cooling trend during those years....to now a clear warming trend. The greatest overall chilling adjustments were made to the October thru December months. But 100% of all months for all years were chilled for April through October. February had the least number of months chilled with 75 of the 89 months while January and March both saw chilling adjustments to 78 of the 89 months on record.

Very disappointing rain totals across the county yesterday and today. Most spots were under 0.10" of rain. There are still some rain chances today but dry does beget dry so not real optimistic. We "dry out" tomorrow and start to heat up with widespread 90's again likely by Monday through Wednesday before sharply cooler to near to below normal by Thursday. Chester County records for today: High 97 degrees at West Chester and Coatesville (1954)/ Low 50 degrees at Phoenixville (1974) / Rain 6.20" at Devault (1975)

Very disappointing rain totals across the county yesterday and today. Most spots were under 0.10" of rain. There are still some rain chances today but dry does beget dry so not real optimistic. We "dry out" tomorrow and start to heat up with widespread 90's again likely by Monday through Wednesday before sharply cooler to near to below normal by Thursday. Chester County records for today: High 97 degrees at West Chester and Coatesville (1954)/ Low 50 degrees at Phoenixville (1974) / Rain 6.20" at Devault (1975)

Thanks Charlie this is great! I have just started downloading this data and will add it to my data set and use it for more analytics and review. Thanks again!

We had some light rain earlier with more just entering the county from the south. We should see a few rounds of rain some heavy through tonight into tomorrow morning. Many spots could pick up at least 1" to 2" of rain - higher amounts are possible. With the rain temps will be a bit below average (83 degrees) today. We dry out and heat up again by Sunday. Chester County records for today: High 104 degrees at Phoenixville (1936) / Low 45 degrees also at Phoenixville (1945) / Rain 4.02" at KMQS Coatesville Airport (2013)

We had some light rain earlier with more just entering the county from the south. We should see a few rounds of rain some heavy through tonight into tomorrow morning. Many spots could pick up at least 1" to 2" of rain - higher amounts are possible. With the rain temps will be a bit below average (83 degrees) today. We dry out and heat up again by Sunday. Chester County records for today: High 104 degrees at Phoenixville (1936) / Low 45 degrees also at Phoenixville (1945) / Rain 4.02" at KMQS Coatesville Airport (2013)

Thanks Charlie I am still not clear is the above the NCEI adjustments to the data for the entire county or for Coatesville? I have not found the individual station adjustments yet. If the above is just for Coatesville can you send me the link to that site? . I would like to see the bias adjustments for Phoenixville and West Chester etc. individually for comparison purposes and adds to my data set. Thanks!

LOL Charlie and I have been doing this for years! If folks don't like it let's start another thread....or just ignore me (could be best solution)

It's more a passion than a job for my team! My human resource team includes a checkbox on the intake form that actually asks the following question (this is directly lifted from the form) Do you believe in climate change (yes) (no) If they answer no and are a self identified climate denier - my HR Director immediately puts them in the left pile (left does not move forward in the process) We refuse to hire climate deniers as climate change is real and of course a stone cold fact!!

Would you like to join our growing team Tim???

The we represents the entire Chester County Weather Team including our statisticians, IT team to support the website and FB page etc.

All about (plural) accuracy (plural) and in plurality of stations (plural) LOL!!!!!

Maybe I run out there with ice packs and wrap the station to chill the thermometer????

My rooftop (poorly sited) Tempest weather station also completely defies diurnal temperature trends and consistently stalls or drops a couple degrees between noon and 1pm see below for July 10th

Can you show me the exact bias adjustment made to the Coatesville obs (not for all of Chester County) if there was a cool bias....why did NOAA with their adjustments for Chester County take the temperature lower than all stations in the county for many of those years?? Wouldn't they have adjusted the temps up for the cool bias??

At 8am is not a big deal as we have shown before....minor to no issues.....6pm for 3 years....no big deal

Max sun and then the 24-hour Davis VP2 Fan Aspiration Radiation Shield kicks in for maximum accuracy