ChescoWx

Our uncomfortably warm weather continues with additional chances of some showers and thunderstorms later today. Tomorrow looks to be the hottest day in this stretch with temperatures well into the 80's and even some 90's in more valley locations. Temperatures will remain above normal this week before falling back close to normal by Friday.

Our uncomfortably warm weather continues with additional chances of some showers and thunderstorms later today. Tomorrow looks to be the hottest day in this stretch with temperatures well into the 80's and even some 90's in more valley locations. Temperatures will remain above normal this week before falling back close to normal by Friday.

I saw on the news one of the local weather folks mentioning we are about to see our 6th "Heatwave" which is a stat that defines a Heatwave of at least 3 consecutive days over 90 degrees. While the news always just sources the Philadelphia International Airport....out here where we live in Chester County only 1 station at Phoenixville has reported even 3 heatwaves this summer with all other stations only 1 or 2 "Heatwaves". As you can see below the frequency of heat waves here in Chester County has in reality been decreasing over the last 14 decades as the below chart which is normalized "per 100 station-years" because the number of active stations has grown sharply over time clearly shows.

I saw on the news one of the local weather folks mentioning we are about to see our 6th "Heatwave" which is a stat that defines a Heatwave of at least 3 consecutive days over 90 degrees. While the news always just sources the Philadelphia International Airport....out here where we live in Chester County only 1 station at Phoenixville has reported even 3 heatwaves this summer with all other stations only 1 or 2 "Heatwaves". As you can see below the frequency of heat waves here in Chester County has in reality been decreasing over the last 14 decades as the below chart which is normalized "per 100 station-years" because the number of active stations has grown sharply over time clearly shows.

Hey Mike, no problem. I went outside of Chester County to find "neighborhood" stations within 30 miles of Coatesville1SW with enough consistent overlapping observations from 1941-1975. We found 6 potential additional “neighborhood” stations but only 2 had enough consistent data Holtwood and Ephrata over the years in question to add to the 3 main Chester County stations above. So what did the analysis find? All 5 raw stations (Coateville 1SW / West Chester 2NW/ Phoenixivlle 1E / Holtwood and Ephrata move together at the same statistically same cooling rate for the same years from 1941-1975 so there is no inconsistent cooling or warming trend for the control station in this analysis (Coatesville 1SW) based on the raw data across these stations. However, as we have found before - the overall NCEI Adjusted Chester County data while following the raw average temperature pattern consistently applied a solid ~1-3 F post hoc adjustment to Coatesville 1SW and all of the 5 stations were chilled by NCEI lower than any of the 5 in the NCEI Chester County wide adjusted annual average temperatures. So for essentially the entire period! This was a clear offset, not a trend divergence. So again what station if not a neighboring station within 30 miles of Chester County was NCEI using to apply non-stop chilling adjustments to Coatsville 1SW to adjust the raw temperatures to even lower levels than they were all showing for all those years? So we know Coatesville 1SW was not adjusted cooler due to Time of Observation bias that was ruled out by majority 8am readings (if anything one could argue for a slight warming adjustment for homogenization) No station moves resulted in significant temperatures changes that were not statistically the same as the other area station trends so we still have no support for the individual Coatesville1SW chilling NCEI adjustments and no support for the overall Chester County historical 1941-1975 chilling adjustments made by NCEI.

We have had quite a wet start to August with most spots seeing between 1.8" to around 3 inches of rain over the last 5 days. Some additional shower chances are possible later today and again on Friday night. We should finally dry out by Sunday. Early next week it starts hot with a chance for some of our valley locations to possibly reach 90 degrees both Monday and Tuesday. Could those be the last chances of a 90-degree reading till next spring?

We have had quite a wet start to August with most spots seeing between 1.8" to around 3 inches of rain over the last 5 days. Some additional shower chances are possible later today and again on Friday night. We should finally dry out by Sunday. Early next week it starts hot with a chance for some of our valley locations to possibly reach 90 degrees both Monday and Tuesday. Could those be the last chances of a 90-degree reading till next spring?

Thanks for the great info @Mike Cyclebut the statistical analysis showed us that there were no unusual temperature changes at Coatesville 1SW that were not statistically aligned with the nearby stations within 30 miles of that point to support. This supports the fact that there was no need for any adjustments to the raw data at all!

Today will be the most pleasant day of the week with low relative humidity and temperatures not too far from normal for early August. Shower chances increase again later tomorrow and additional chances remain for the rest of the work week. No total washouts but plenty of shower chances.

Today will be the most pleasant day of the week with low relative humidity and temperatures not too far from normal for early August. Shower chances increase again later tomorrow and additional chances remain for the rest of the work week. No total washouts but plenty of shower chances.

Below is the Chester County PA Climate Summary for July 2026. We finished the month with an average temperature of 75.0 this is 0.8 degrees below normal our average rainfall across the county was 4.36". This was our "chilliest" July since the 74.9 in 2021. Overall we finished as the 61st warmest and 66th driest July over the last 134 years. Our warmest July was the 78.7 in 1999 our coolest July was back in 2009 with an average temperature of only 70.9 degrees. Our wettest on average was the 11.64" average across the county way back in 1919. The dryest on average July was the scant 0.68" average back in 1944. Overall through the first 7 months of 2026 we have an average temperature to date of 51.9 degrees this is 0.5 degrees below the average over the last 30 years and the 61st warmest first 7 months since records began in 1893.

Below is the Chester County PA Climate Summary for July 2026. We finished the month with an average temperature of 75.0 this is 0.8 degrees below normal our average rainfall across the county was 4.36". This was our "chilliest" July since the 74.9 in 2021. Overall we finished as the 61st warmest and 66th driest July over the last 134 years. Our warmest July was the 78.7 in 1999 our coolest July was back in 2009 with an average temperature of only 70.9 degrees. Our wettest on average was the 11.64" average across the county way back in 1919. The dryest on average July was the scant 0.68" average back in 1944. Overall through the first 7 months of 2026 we have an average temperature to date of 51.9 degrees this is 0.5 degrees below the average over the last 30 years and the 61st warmest first 7 months since records began in 1893.

A pretty unsettled weather week on the way with shower chances increasing later today and becoming likely tonight into tomorrow. No washouts except for most likely tomorrow. Tuesday and Thursday look to be the relatively driest days before rain chances increase again to close out the work week. Temperatures this week are close to normal for the start of August.

A pretty unsettled weather week on the way with shower chances increasing later today and becoming likely tonight into tomorrow. No washouts except for most likely tomorrow. Tuesday and Thursday look to be the relatively driest days before rain chances increase again to close out the work week. Temperatures this week are close to normal for the start of August.

This is a follow up to the earlier Coatesville 1SW review and analysis. The issue surfaced earlier and evaluated further here is to determine if there is support for the NCEI post hoc chilling of all raw data for the consistently reporting Chester County PA stations of Coatesville1SW/ West Chester 2NW and Phoenixville1E from 1941-1975? Keep in mind that without these NCEI chilling adjustments the long-term average annual temperature warming curve for Chester County goes from significant warming based on NCEI adjusted data to clear non statistical warming from 1893 through 2025. So for this pass we went outside of Chester County to find "neighborhood" stations within 30 miles of Coatesville1SW with enough consistent overlapping observations from 1941-1975. We found 6 potential additional “neighborhood” stations but only 2 had enough consistent data Holtwood and Ephrata over the years in question to add to the 3 main Chester County stations above. So what did the analysis find? All 5 raw stations move together in the same years so there is no inconsistent cooling trend based on the raw data across these stations. However, as we have found before - the overall NCEI Adjusted Chester County data while following the raw average temperature pattern consistently applied a solid ~1-2 F post hoc adjustment that was in fact below all 5 raw stations across essentially the entire period! This was a clear offset, not a trend divergence. So again what station if not a neighboring station within 30 miles of Chester County was NCEI using to apply non-stop chilling adjustments to adjust the raw temperatures to even lower levels than they were all showing for all those years? So we know Coatesville 1SW was not adjusted cooler due to Time of Observation bias that was ruled out by majority 8am readings (if anything one could argue for a slight warming adjustment for homogenization) No station moves resulted in significant temperatures changes that were not statistically the same as the other area station trends so we still have no support for the individual Coatesville1SW chilling NCEI adjustments and no support for the overall Chester County historical 1941-1975 chilling adjustments made by NCEI. See chart attached.

Here in East Nantmeal July finished with a slight 0.3 below normal average temperature for the month. This was the 4th below average month across our first 7 months of 2026. I will have the Chester County wide month summary later today. We turn a bit more humid today with rain chances again increasing by tomorrow night and lasting through much of the upcoming work week. No total washouts but a chance at some much-needed rainfall for areas who missed the beneficial rains last week.

Here in East Nantmeal July finished with a slight 0.3 below normal average temperature for the month. This was the 4th below average month across our first 7 months of 2026. I will have the Chester County wide month summary later today. We turn a bit more humid today with rain chances again increasing by tomorrow night and lasting through much of the upcoming work week. No total washouts but a chance at some much-needed rainfall for areas who missed the beneficial rains last week.

If anyone is interested in where the 19 current stations that feed our current active philly burbs of Chester County PA area weather data below is a map along with what type of station/reporter they have. Let me know if any questions. Thanks! There is also an interactive map with more detailed station detail that you can hover over on the ChescoWx website at https://chescowx.com/detailed-station-data/

If anyone is interested in where the 19 current stations that feed our current active philly burbs of Chester County PA area weather data below is a map along with what type of station/reporter they have. Let me know if any questions. Thanks! There is also an interactive map with more detailed station detail that you can hover over on the ChescoWx website at https://chescowx.com/detailed-station-data/ https://on-data/@DrewForecast

You limited your local review to only 3 chesco stations - My review with AI had more local stations than you including Sadsbury, Devault 1W, Kennett Square and Morgantown- I focused on only local stations in or on the immediate borders of chesco like Morgantown/Elverson to better identify if there is any actual support based on the raw data that was able to identify if any significant drifts occurred at any stations near Coatesville 1SW to suppor the NCEI chilling adjustments. The statistical analysis clearly does not support the NCEI adjustments for Coatesville 1SW

Our great weather continues with temperatures not far from normal as we close out July and move into August. Our next rain chances start to increase by Sunday.

Our great weather continues with temperatures not far from normal as we close out July and move into August. Our next rain chances start to increase by Sunday.

Our weather has trended nicer for much of the rest of the work week with below normal temperatures continuing through the period. OUr next rain chances look to arrive later Sunday and into the start of the new work week.

Our weather has trended nicer for much of the rest of the work week with below normal temperatures continuing through the period. OUr next rain chances look to arrive later Sunday and into the start of the new work week.

Hi Don, I made no references at all to NCEI adjustments - the program identified the NCEI adjusted data. I had it review the NCEI adjustment criteria and assess based on those thresholds how the actual vs raw data surrounding changes for either TOB or site moves matched the critiera established by NCEI based on the adjustment papers.