Central PA Summer 2026 Discussion/Obs Thread

[canderson]

MDT’s low was 81. I’d think that is very close to record high low. 
 

It’s 92 at 9:40. Today may be hotter than yesterday. 

[Eskimo Joe]

2 minutes ago, canderson said:

MDT’s low was 81. I’d think that is very close to record high low. 
 

It’s 92 at 9:40. Today may be hotter than yesterday. 

If storms don't fire up today, a lot of record low minimums are in jeopardy all along the Acela corridor.

[Superstorm]

Managed to get to 77F for a low.

Already up to 89F.


.

[canderson]

11 minutes ago, Eskimo Joe said:

If storms don't fire up today, a lot of record low minimums are in jeopardy all along the Acela corridor.

Yea there won’t be any storms aside tiny popup miracle ones. 
 

Even Sunday’s rain is looking grim. 

[ChescoWx]

The low here in East Nantmeal was only 77.2 degrees. This is the 3rd highest minimum temperature since 2004. Another hot day today with temperatures close to what they were yesterday - mid 90's to near 100 degrees. Small chances of some showers tonight and we begin to slowly trim the heat with highs tomorrow closer to the mid-90's. Shower at T-storm chances ramp up later tomorrow and at night. We then fall back closer to normal temperatures on Sunday before we trend to below normal temperatures by both Monday and Tuesday.

[Voyager]

1 hour ago, Eskimo Joe said:

 

Literal once in a lifetime event. This thing will likely never come east again.

Exactly. That's why I went. Of course it wasn't as bad at 11am in Tamaqua as it was in the afternoon farther south toward Reading and beyond.

[Itstrainingtime]

Yesterday I reached 93 at 9:35am. Today it was 10:45. Running a good 2-3 degrees lower than yesterday. 

[CarlislePaWx]

Yesterday afternoon around 2:30 I was driving up 81 to 83 to Union Deposit for a doctor appointment.  On the way up my car thermo was fluctuating between 103 and 104.  As if that weren't stunning enough, about an hour later heading back to Carlisle via the same route, the thermo had reached 106 degrees!  It read that when I got in the car to leave and then fluctuated between 105 and 106 until just before the MIddlesex exit when it read 104 for almost the remainder of my trip home  When I arrived back home around 4:00pm my backyard temp read 100.6 and then proceeded to peak at 102.0 degrees.  This reading is the highest reading I've recorded in the Carlisle area since moving here in 2000 (almost 26 years ago next month). 

My high on Thursday was 100.4 degrees.  Currently, at 10:51am the temperature is 94.5 degrees with a dew point of 79.0 and a heat index of 112.0.  This is a higher dew point than recorded yesterday.  I'm wondering if I'll break 102 and or a heat index of 120?  Peak heat index Wednesday was 119.5.  My low this morning was 76.1 while yesterday morning's low was 73.6 degrees.

[canderson]

95 at 10:50 a.m. My humidity sensor is broken but it feels dangerous out. 

[Blizzard of 93]

There is a slight occasional breeze, which is helping a small bit in partially shaded areas.

[Jns2183]

The low here in East Nantmeal was only 77.2 degrees. This is the 3rd highest minimum temperature since 2004. Another hot day today with temperatures close to what they were yesterday - mid 90's to near 100 degrees. Small chances of some showers tonight and we begin to slowly trim the heat with highs tomorrow closer to the mid-90's. Shower at T-storm chances ramp up later tomorrow and at night. We then fall back closer to normal temperatures on Sunday before we trend to below normal temperatures by both Monday and Tuesday.

Hey, I pulled together the estimated PRISM grid coverage and climate data package for Chester County.

PRISM is a gridded climate dataset from Oregon State University’s PRISM Climate Group. Instead of only using individual weather stations, PRISM takes station observations, terrain, elevation, coastal effects, and other geographic factors into account to estimate climate variables across a continuous grid. It is commonly used for precipitation, temperature, dew point, vapor pressure deficit, solar/climate analysis, drought work, agricultural analysis, hydrology, and local climate comparisons.

For Chester County, I estimated the county intersects about 151 PRISM-style 4 km grid cells.

Each 4 km grid cell is:

4,000 meters wide by 4,000 meters tall

About 2.49 miles wide by 2.49 miles tall

16 square kilometers

About 6.18 square miles

The coordinate file I made gives the estimated centerpoint of each 4 km cell covering at least part of Chester County. The file is latitude, longitude format with no header row, so it should be easy to paste into mapping tools, GIS software, or scripts.

The ZIP file size is about 58 MB.

Unzipped, the data is about 208 MB.

What is included in the data package:

Daily PRISM files from 1981 through July 1, 2026

Monthly PRISM files from 1895 through May 2026

1991–2020 monthly normals

1991–2020 daily normals

The daily files are the day-by-day weather/climate estimates for each Chester County grid cell. These are useful for looking at specific storms, heat waves, cold snaps, wet/dry stretches, day-to-day variability, growing season conditions, and longer-term local trends.

The monthly files go much farther back, starting in 1895 and running through May 2026. These are better for long-term climate history because they cover more than 130 years. They are useful for comparing recent months to the historical record, ranking wet/dry months, looking at long-term warming trends, and comparing different decades.

The 1991–2020 monthly normals are the modern 30-year baseline averages. These tell you what is “normal” for each month at each grid cell, using the current standard climate-normal period.

The 1991–2020 daily normals are the day-of-year baseline values. These are useful when you want to compare a specific date, like July 1 or October 15, against what is normally expected for that time of year.

The main variables included or represented are:

ppt: precipitation

tmin: minimum temperature

tmean: mean temperature

tmax: maximum temperature

tdmean: mean dew point temperature

vpdmin: minimum vapor pressure deficit

vpdmax: maximum vapor pressure deficit

Depending on the specific PRISM product set, solar-related variables may also be available:

solclear: clear-sky solar radiation

soltotal: total solar radiation on a horizontal surface

solslope: solar radiation adjusted for slope/aspect

soltrans: cloud transmittance

The temperature variables are useful for heat, cold, frost, growing season, and general climate work.

The precipitation variable is useful for rainfall/snow-water equivalent, storm totals, drought, wet spells, and long-term precipitation trends.

Dew point is useful because it describes actual atmospheric moisture better than relative humidity alone. It helps show humid-air events, muggy periods, and moisture transport.

Vapor pressure deficit, or VPD, is useful for plant stress, evaporation demand, drought stress, and agricultural or ecological analysis. Higher VPD generally means the atmosphere is pulling moisture more aggressively from plants and surfaces.

There is also a finer 800 meter PRISM grid option. The relationship is simple: one 4 km cell can be divided into 25 smaller 800 m cells, because 4,000 meters divided by 800 meters is 5 cells across, and 5 by 5 equals 25.

So one 4 km cell equals:

5 smaller 800 m cells across

5 smaller 800 m cells tall

25 total 800 m cells inside one 4 km cell

Each 800 m grid cell is:

800 meters wide by 800 meters tall

About 0.50 miles wide by 0.50 miles tall

0.64 square kilometers

About 0.247 square miles

For Chester County, the rough 800 m estimate is around 3,300 cells if counting cells that touch the county boundary. If you simply subdivided all 151 estimated 4 km cells into 25 smaller cells each, that would be 3,775 possible 800 m subcells, but the more realistic county-clipped estimate is closer to 3,300 because the county boundary cuts through edge cells.

The 800 m version would give much more local detail, especially in areas where terrain, elevation, urbanization, valleys, or county-edge effects matter. It would also be much larger. Since 800 m resolution has 25 times as many grid cells as 4 km resolution, the same date range and variables could be up to roughly 25 times larger.

As a rough estimate, if the 4 km package is 58 MB zipped and 208 MB unzipped, the equivalent 800 m package could be somewhere around:

1.45 GB zipped

5.2 GB unzipped

That is only a rough scaling estimate, because compression varies by variable and file structure, but it gives the right ballpark.

I started with the 4 km version because it is much smaller, easier to transfer, and still gives a good countywide climate picture. If you want the higher-detail 800 m version, I can pull/build that too.

Link to 4km
https://drive.google.com/file/d/1uD5Q3O_voxpLItJHbWMpdAkgKtBMc-k0/view?usp=drivesdk

Sent from my SM-S731U using Tapatalk

[Jns2183]

Exactly. That's why I went. Of course it wasn't as bad at 11am in Tamaqua as it was in the afternoon farther south toward Reading and beyond.

Everything I did for chester I've done for Schyukhill also, except at 800m grid . Over 3600 grid cells. By weekend end I should have a fun little expose on the wild and wacky climate up there

Sent from my SM-S731U using Tapatalk

[canderson]

KMDT hit 100 before noon. Insanity 

[Itstrainingtime]

7 minutes ago, canderson said:

KMDT hit 100 before mom. Insanity 

Wow! I'm just one degree lower than yesterday at noon. I seem to be catching up...

[ChescoWx]

28 minutes ago, Jns2183 said:

Hey, I pulled together the estimated PRISM grid coverage and climate data package for Chester County.

PRISM is a gridded climate dataset from Oregon State University’s PRISM Climate Group. Instead of only using individual weather stations, PRISM takes station observations, terrain, elevation, coastal effects, and other geographic factors into account to estimate climate variables across a continuous grid. It is commonly used for precipitation, temperature, dew point, vapor pressure deficit, solar/climate analysis, drought work, agricultural analysis, hydrology, and local climate comparisons.

For Chester County, I estimated the county intersects about 151 PRISM-style 4 km grid cells.

Each 4 km grid cell is:

4,000 meters wide by 4,000 meters tall

About 2.49 miles wide by 2.49 miles tall

16 square kilometers

About 6.18 square miles

The coordinate file I made gives the estimated centerpoint of each 4 km cell covering at least part of Chester County. The file is latitude, longitude format with no header row, so it should be easy to paste into mapping tools, GIS software, or scripts.

The ZIP file size is about 58 MB.

Unzipped, the data is about 208 MB.

What is included in the data package:

Daily PRISM files from 1981 through July 1, 2026

Monthly PRISM files from 1895 through May 2026

1991–2020 monthly normals

1991–2020 daily normals

The daily files are the day-by-day weather/climate estimates for each Chester County grid cell. These are useful for looking at specific storms, heat waves, cold snaps, wet/dry stretches, day-to-day variability, growing season conditions, and longer-term local trends.

The monthly files go much farther back, starting in 1895 and running through May 2026. These are better for long-term climate history because they cover more than 130 years. They are useful for comparing recent months to the historical record, ranking wet/dry months, looking at long-term warming trends, and comparing different decades.

The 1991–2020 monthly normals are the modern 30-year baseline averages. These tell you what is “normal” for each month at each grid cell, using the current standard climate-normal period.

The 1991–2020 daily normals are the day-of-year baseline values. These are useful when you want to compare a specific date, like July 1 or October 15, against what is normally expected for that time of year.

The main variables included or represented are:

ppt: precipitation

tmin: minimum temperature

tmean: mean temperature

tmax: maximum temperature

tdmean: mean dew point temperature

vpdmin: minimum vapor pressure deficit

vpdmax: maximum vapor pressure deficit

Depending on the specific PRISM product set, solar-related variables may also be available:

solclear: clear-sky solar radiation

soltotal: total solar radiation on a horizontal surface

solslope: solar radiation adjusted for slope/aspect

soltrans: cloud transmittance

The temperature variables are useful for heat, cold, frost, growing season, and general climate work.

The precipitation variable is useful for rainfall/snow-water equivalent, storm totals, drought, wet spells, and long-term precipitation trends.

Dew point is useful because it describes actual atmospheric moisture better than relative humidity alone. It helps show humid-air events, muggy periods, and moisture transport.

Vapor pressure deficit, or VPD, is useful for plant stress, evaporation demand, drought stress, and agricultural or ecological analysis. Higher VPD generally means the atmosphere is pulling moisture more aggressively from plants and surfaces.

There is also a finer 800 meter PRISM grid option. The relationship is simple: one 4 km cell can be divided into 25 smaller 800 m cells, because 4,000 meters divided by 800 meters is 5 cells across, and 5 by 5 equals 25.

So one 4 km cell equals:

5 smaller 800 m cells across

5 smaller 800 m cells tall

25 total 800 m cells inside one 4 km cell

Each 800 m grid cell is:

800 meters wide by 800 meters tall

About 0.50 miles wide by 0.50 miles tall

0.64 square kilometers

About 0.247 square miles

For Chester County, the rough 800 m estimate is around 3,300 cells if counting cells that touch the county boundary. If you simply subdivided all 151 estimated 4 km cells into 25 smaller cells each, that would be 3,775 possible 800 m subcells, but the more realistic county-clipped estimate is closer to 3,300 because the county boundary cuts through edge cells.

The 800 m version would give much more local detail, especially in areas where terrain, elevation, urbanization, valleys, or county-edge effects matter. It would also be much larger. Since 800 m resolution has 25 times as many grid cells as 4 km resolution, the same date range and variables could be up to roughly 25 times larger.

As a rough estimate, if the 4 km package is 58 MB zipped and 208 MB unzipped, the equivalent 800 m package could be somewhere around:

1.45 GB zipped

5.2 GB unzipped

That is only a rough scaling estimate, because compression varies by variable and file structure, but it gives the right ballpark.

I started with the 4 km version because it is much smaller, easier to transfer, and still gives a good countywide climate picture. If you want the higher-detail 800 m version, I can pull/build that too.

Link to 4km
https://drive.google.com/file/d/1uD5Q3O_voxpLItJHbWMpdAkgKtBMc-k0/view?usp=drivesdk

Sent from my SM-S731U using Tapatalk
 

This is excellent thank you!! I have looked at this in the past but you have really detailed and packaged this nicely!!! most appreciated!! I will dive into this!!

[Eskimo Joe]

Harrisburg (MDT) hits 100°

[ChescoWx]

Below is the June and 1st Half of 2026 Chester County Area Climate Summary. Overall the county finished with a slightly above average temperature of 70.8 degrees or 0.6 degrees above the 1991-2020 climate baseline for June of 70.2 degrees. When using the entire climate dataset since 1893 we finished only +0.4 degrees above our overall 134 year average June temperature which is 70.4. This was 1.2 degrees cooler than June 2025 and our coolest June since the 67.4 degree average in June 2023. This was our 61st warmest June over the last 134 years of county climate data. Through the 1st 6 months of the year our average temperature was 48.0 degrees. This is 0.4 degrees below the 1991-2020 baseline and 0.1 degree over the 1893 - 2025 baseline. This represents our coldest start to a year since 2015. Overall this is the 66th warmest 1st half of a year over the last 134 years. Average precipitation across all stations was 3.11" this is 1.20" the 1991-2020 baseline and 1.02" below the overall average since 1893. For the 1st half of the year county precipitation has averaged 15.34" this is 6.95" below the 1991-2020 baseline of 22.29" and 6.82" below the 1893-2026 all years average of 22.16". This is our 7th driest average precipitation total with the lowest being the 13.82" average for the first half of 1963.

[Itstrainingtime]

98 currently. 3 below yesterday. No idea why, sure as hell ain't complaining.

[RCC]

It would be nice for most of the rest of us if the Chester County Pa trivia was taken elsewhere. It’s not close to central Pa.  Just keeping it real. Thanks. 

[Mount Joy Snowman]

We arrived a bit ago out here in the rural stretches of southwestern Westmoreland County. Highest car thermo reading on the drive out was 96 at various spots through the Cumberland Valley, low was 88 at three different spots — the top of the high hill on the Fulton/Bedford line, through the high points of Somerset, and right as we arrived down here in sticks. Nice breeze blowing out here too, still hot but much more bearable than back home. 

[ChescoWx]

East Nantmeal current temp is 92.7 the high has been 93.0. This is the 3rd consecutive day  I have reached 90 degrees. This marks only the 8th "heatwave" I have recorded in my 23 summers here in EN since 2004. Of note my poorly sited rooftop Tempest has gone 95.4 / 98.2 / 94.8 the last 3 days vs my VP Pro 2 with 93.0/94.8/91.0

[Itstrainingtime]

10 minutes ago, Mount Joy Snowman said:

We arrived a bit ago out here in the rural stretches of southwestern Westmoreland County. Highest car thermo reading on the drive out was 96 at various spots through the Cumberland Valley, low was 88 at three different spots — the top of the high hill on the Fulton/Bedford line, through the high points of Somerset, and right as we arrived down here in sticks. Nice breeze blowing out here too, still hot but much more bearable than back home. 

Sounds wonderful. 100 on the nose here. Enjoy the weekend.

[Mount Joy Snowman]

9 minutes ago, Itstrainingtime said:

Sounds wonderful. 100 on the nose here. Enjoy the weekend.

Thank you, same to you! I should add that things are MUCH greener out this way too, unsurprisingly. 

[Eskimo Joe]

Lancaster (LNS) hits 100°.