Summer heatJune to August 2026NOAA daily records
Summer 2026 was the fourth warmest at Philadelphia's airport since 1941, with three straight days above 100°F
June, July and August averaged 78.8°F at Philadelphia International Airport. Only 2010, 2022 and 2016 ran warmer in the 86 summers of NOAA's record there, and the airport reached 103°F, 102°F and 101°F on July 2 to 4.
- Average temperature
- 78.8°FFourth warmest of 86 summers
- Days at 90°F or hotter
- 341991 to 2020 average: 25.8
- Hottest reading
- 103°FJuly 2
- Nights at 75°F or warmer
- 151991 to 2020 average: 9.9
The airport topped 90°F on 34 days from June to August, and on three days in a row in July it passed 100°F
June, July and August 2026 averaged 78.8°F at Philadelphia International Airport, the fourth warmest summer of the 86 in NOAA's record there since 1941. Only 2010, 2022 and 2016 ran warmer. The average is the mean of each day's high and low, taken from the station's daily record through August 31 with no days missing. The summer also brought 34 days at 90°F or hotter, against an average of 25.8 in the summers of 1991 to 2020, and three days in a row above 100°F, from July 2 to July 4.
2026 averaged 78.80°F, fourth behind 2010, 2022 and 2016
Only one summer reading since 1941 topped July 2's 103°F
The airport reached 103°F on July 2, 102°F on July 3 and 101°F on July 4. Since 1941, only one summer reading has been higher, 104°F on July 3, 1966, and 103°F has been reached in three other summers: 1995, 2010 and 2011.
Four other summers had three or more days at 100°F or hotter. 1957, 1966 and 1993 had three each, and 1988 had five. No summer since 1993 had as many.
Five summers have had three or more days at 100°F, and 2026 is the first since 1993
| Summer | Days at 100°F+ | Hottest | Date |
|---|---|---|---|
| 1957 | 3 | 101°F | Jul 21 |
| 1966 | 3 | 104°F | Jul 3 |
| 1988 | 5 | 102°F | Jul 17 |
| 1993 | 3 | 101°F | Jul 10 |
| 2026 | 3 | 103°F | Jul 2 |
The heat was spread across the season. June had 11 days at 90°F or hotter, July 10 and August 13. August had the most 90-degree days but none at 95°F, and July had six of the summer's eight days at 95°F or hotter. The longest run of 90-degree days lasted seven days, starting June 29. Two more 90-degree days came in September.
Nights stayed warm too. The low held at 75°F or warmer on 15 nights. Summers from 1941 to 1970 averaged 2.4 such nights, and summers from 1991 to 2020 averaged 9.9. On July 3 the low was 82°F.
The 2020s have averaged 32.9 days at 90°F a summer, against 14.6 in the 1960s
The count of 90-degree days varies a lot from one summer to the next. 2023 had 17 and 2025 had 36. Averaged by decade, the 1960s had the fewest, 14.6 a summer, and the 2010s had 28.8. The seven summers from 2020 through 2026 have averaged 32.9.
Summers at the airport have brought more 90-degree days since the 1960s, and 2026 had 34
Norristown, about 3 miles from the borough, had 18 days at 90°F to the airport's 34
The airport sits at an elevation of 7 feet and is about 15 miles from Conshohocken, by the station coordinates ACIS lists. NOAA's Norristown station, USC00366370, is about 3 miles from the borough at an elevation of 62 feet. It belongs to the Cooperative Observer Program, where an observer reads the thermometer once a day, and ACIS lists its summer 2026 readings as taken at 6 or 7 a.m. Each Norristown day ends that morning, so an afternoon high shows up under the next day's date.
Norristown's 101°F readings are dated a day after the airport's peak
Norristown had no missing days from June through August. It recorded 18 days at 90°F or hotter, seven at 95°F or hotter and three at 100°F or hotter. Its top reading was 101°F, dated July 3 and July 4, and it recorded 100°F dated July 5. Those match the airport's July 2 to 4 heat, shifted by the morning reading. Its summer averaged 76.15°F, and six of its nights stayed at 75°F or warmer.
Both stations had three days at 100°F, and the airport had more of every other kind of hot day
| June to August 2026 | Airport | Norristown |
|---|---|---|
| Days at 90°F or hotter | 34 | 18 |
| Days at 95°F or hotter | 8 | 7 |
| Days at 100°F or hotter | 3 | 3 |
| Nights at 75°F or warmer | 15 | 6 |
| Hottest reading | 103°F | 101°F |
| Average temperature | 78.80°F | 76.15°F |
| Days missing | 0 | 0 |
A dark roof in summer sun can reach 150°F or more
These figures are air temperatures. A roof in the sun runs much hotter. The U.S. Department of Energy's 2010 guide to cool roofs says traditional dark roofs can reach 150°F or more in summer sun, and that most dark roofing materials reflect only 5 to 20% of sunlight. Light-colored materials reflect 55 to 90%, by the same guide's figures.
A poorly vented attic can reach 140°F on a 90°F day, and a dark roof 150°F or more
Most dark roofing reflects 5 to 20% of sunlight, and light-colored roofing 55 to 90%
Under the roof, the Asphalt Roofing Manufacturers Association (ARMA), the shingle makers' trade group, says a poorly ventilated attic can reach 140°F on a 90°F day. In a 2023 technical bulletin it says heat buildup in an attic may accelerate the aging of asphalt roofing products. Its 2022 article adds that an overheated attic, combined with moisture, can distort shingles and damage the roof deck, the plywood or boards the shingles are nailed to.
Heat also changes how a roof should be installed and repaired. ARMA's hot-weather bulletin says shingles soften and scuff under foot traffic in hot weather and become more flexible, so rough handling can tear them. It advises installing early on hot, sunny days and working the west- and south-facing slopes in the morning.
Most shingles carry a strip of sealant that bonds each course to the one below once the sun heats it, so a new roof seals itself in summer. That same bond makes repairs harder on an older roof in hot weather: ARMA says pulling up sealed shingles may tear them, and suggests waiting until the shingles are cooler or misting them with water first.
What to ask before you sign
Ask how the attic will be vented and how much vent area the roofer is installing. Vent area is measured as net free area, the open space air can pass through once screens and louvers are counted. Section R806.2 of the 2021 International Residential Code, which Conshohocken's re-roofing addendum cites, sets a minimum of 1/150 of the vented space. It allows 1/300 when 40 to 50% of the vent area sits in the upper part of the attic, within 3 feet of the ridge, with the rest in the bottom third. In the coldest climate zones, 6 through 8, that exception also requires a vapor retarder on the warm side of the ceiling.
A 900-square-foot attic floor, with round numbers
Each square is 1 square foot of net free area, at the two ratios in Section R806.2.
As an example with round numbers, a 900-square-foot attic floor needs 6 square feet of net free area at 1/150, or 3 square feet at 1/300. ARMA recommends that intake vents at the eaves make up 50 to 60% of the total and exhaust vents near the ridge 40 to 50%, and says intake should never be less than exhaust.
Conshohocken's addendum asks the applicant whether the space under the roof is vented and whether the owner was told that a lack of adequate venting may void the manufacturer's warranty. Read that answer before you sign the addendum. The addendum states the venting rule in slightly different terms from the 2021 code text, so if your attic is close to the line, ask the borough's Licenses and Inspections office at 610-828-1092 which version it applies.
If a repair is scheduled in midsummer, ask when the crew will work and how they will lift sealed shingles. The roofing contract guide covers what the written contract has to include, the permits guide covers the addendum and the borough's other forms, and the weather guide covers the area's rain, wind, hail and freeze-thaw.
The last 12 summers at the airport
| Summer | 90°F+ days | Bar of 90°F days | 95°F+ | 100°F+ | Hottest | Nights 75°F+ | Average |
|---|---|---|---|---|---|---|---|
| 2026 | 34 | 8 | 3 | 103°F | 15 | 78.80°F | |
| 2025 | 36 | 8 | 1 | 101°F | 23 | 77.39°F | |
| 2024 | 30 | 14 | 0 | 98°F | 17 | 78.49°F | |
| 2023 | 17 | 2 | 0 | 95°F | 6 | 75.88°F | |
| 2022 | 43 | 9 | 0 | 99°F | 26 | 79.33°F | |
| 2021 | 34 | 6 | 0 | 97°F | 12 | 77.74°F | |
| 2020 | 36 | 7 | 0 | 97°F | 15 | 78.39°F | |
| 2019 | 30 | 5 | 0 | 98°F | 15 | 77.59°F | |
| 2018 | 25 | 6 | 0 | 98°F | 10 | 76.91°F | |
| 2017 | 21 | 3 | 0 | 96°F | 9 | 76.41°F | |
| 2016 | 38 | 11 | 0 | 98°F | 18 | 78.85°F | |
| 2015 | 29 | 4 | 0 | 95°F | 13 | 77.72°F |
Caveats
The National Weather Service says daily observations are preliminary until NOAA's National Centers for Environmental Information finishes quality control, three or more months after they are taken. The July 2 to 4 readings are just over three months old and the August readings about six weeks old, so the counts here could change slightly.
All the figures are air temperatures at two weather stations. They do not measure roof surfaces or attics. ARMA's statements about aging describe heat in general, and none of the sources used here ties a given number of hot days to a shorter shingle life.
The airport record is complete for every summer since 1941. The Norristown record has long gaps in earlier decades, so this article uses it only for summer 2026, and its morning readings make day-by-day comparisons with the airport approximate.