Data | Conshy Roofers

December 2025 had 28 freeze-thaw days at Philadelphia's airport, the most of any month since 1940

Sat, 03 Oct 2026 16:11:58 -0400

Philadelphia International Airport recorded 28 freeze-thaw days in December 2025, more than in any month since the station’s record began in July 1940. That is this site’s count from NOAA’s daily temperature records, and a freeze-thaw day here is one when the low reached 32°F or colder and the high rose above 32°F. The winter as a whole, July 2025 through June 2026, had 70 freeze-thaw days. That is the most since 2018-19 and above the 64.4 average of the 30 winters from 1990-91 to 2019-20, though well short of the 80.1 average from 1941-42 to 1970-71.

Freeze-thaw days at the airport have declined since the 1940s, and 2025-26 brought 70

Freeze-thaw days per winter, July through June, Philadelphia International Airport, 1940-41 to 2025-26. Each bar is labeled with the year its winter ended.

Counted by Conshy Roofers from NOAA daily highs and lows. Source: data.rcc-acis.org

How the count works

The airport station, NOAA’s USW00013739, has a daily high and low for every day from July 1, 1940 through September 30, 2026, with no days missing. For each day, this count checks two things: the low was 32°F or colder, and the high was 33°F or warmer. The record lists whole degrees, so a high above 32°F means 33°F or more. Each winter runs from July 1 through June 30.

The day is the station’s own. The National Weather Service’s Chicago office, describing how airport stations report, says the observation period for a calendar day runs from midnight to midnight local standard time, which is 1 a.m. to 1 a.m. during daylight saving time.

Researchers define freeze-thaw cycles in several ways. The Great Lakes Integrated Sciences and Assessments program (GLISA) at the University of Michigan lists a common one as a day when the high is above 32°F and the low is below it, which leaves out days with a low of exactly 32°F. Under that stricter rule the airport had 61 freeze-thaw days in 2025-26. The decline over the record shows under either rule.

Philadelphia International Airport, the last 12 winters. Freezing nights have a low at or below 32°F. All-day freezes have a high at or below 32°F.
Winter	Freeze-thaw days	Freezing nights	All-day freezes	December
2014-15	68	90	22	9
2015-16	39	49	10	2
2016-17	56	63	7	17
2017-18	67	82	15	10
2018-19	74	81	7	18
2019-20	57	59	2	14
2020-21	67	75	8	17
2021-22	60	68	8	5
2022-23	50	54	4	18
2023-24	50	56	6	10
2024-25	60	74	14	16
2025-26	70	84	14	28

Source: data.rcc-acis.org

December 2025

The low reached 32°F or colder on 29 of December’s 31 days, and the high stayed at or below freezing on only one of them. That left 28 freeze-thaw days. The next highest month in the record is January 1960, with 27. The previous high for a December was 24, reached in 1944 and in 1947.

The rest of the winter ran close to recent averages. January had 16 freeze-thaw days and February 18, against averages of 16.1 for each month in the 1990-91 to 2019-20 winters. March had 5, below its average of 11.2, and November 2, below its 5.4. December’s average over those 30 winters was 14.6, so December 2025 came in at nearly twice its usual count.

The long decline

Freeze-thaw days at the airport fell from an average of 80.1 a winter in 1941-42 to 1970-71 to 70.1 in 1971-72 to 2000-01 and 64.4 in 1990-91 to 2019-20. The last ten winters averaged 61.1. The fewest in the record came in 2015-16, with 39.

A freeze-thaw day is a freezing night that warms above 32°F by afternoon, so each winter’s count equals its freezing nights minus its all-day freezes. Days with a low at or below 32°F averaged 97.3 a winter in 1941-42 to 1970-71 and 69.6 in the last ten winters, a drop of 27.7. Days that stayed at or below freezing all day fell from 17.2 to 8.5, a drop of 8.7. The difference, 19.0 fewer freeze-thaw days a winter, is the decline from 80.1 to 61.1.

Last winter’s 70 ties 2003-04 for eighth among the last 30 winters. Of all 86 winters on record, 45 had more, and in the 1941-42 to 1970-71 period it would have been below the average.

Closer to Conshohocken

The airport sits at an elevation of 7 feet, about 15 miles from Conshohocken by the station coordinates in ACIS. NOAA’s station in Norristown, USC00366370, is under 3 miles away. It belongs to the National Weather Service’s Cooperative Observer Program, where observers record daily high and low temperatures, and its record has long gaps. It also keeps a different day. ACIS lists the Norristown readings as taken at 7 a.m. local standard time in December 2025 and at 8 a.m. in January 1965, so each of its days ends in the morning.

In the 32 winters since 1952-53 when Norristown is missing no more than three days between October and April, it averaged 84.0 freeze-thaw days, against 71.3 at the airport in the same winters. The gap has widened. In the 26 such winters from 1952-53 to 1984-85, Norristown averaged 84.0 and the airport 74.4. In the six from 2012-13 to 2022-23, Norristown averaged 84.2 and the airport 57.8. For 2025-26, Norristown counted 86 with five days missing between October and April, so its full count was at least 86.

Because the two stations end their days at different hours, read the comparison as two records set side by side.

What this means for a roof

GLISA notes that water expands when it freezes, and that repeated freezing, thawing and refreezing can damage roads, sidewalks and other outdoor surfaces. On roofs, the sources this site uses describe specific effects:

The National Park Service’s slate roof brief says slate weathers mainly when impurities in the stone react during wet and dry, hot and cold cycles, and that slate’s low porosity limits the damage frost does to the stone itself.
The Metal Roofing Alliance says concrete tile can crack and warp in the freeze-thaw cycle of northern climates.
Conshohocken’s re-roofing addendum requires ice and water shield to run at least 24 inches inside the exterior wall line when a roof is replaced.

The National Roofing Contractors Association recommends inspecting a roof each spring and fall from the ground or a ladder, looking for curling or split shingles, missing tabs and cracked or missing pieces on slate, tile and metal roofs. The roof inspection checklist lists what to look for, and the weather guide covers the area’s rain, wind and hail.

Caveats

These counts are of air temperature at each station. They are not measurements of a roof’s surface, which this data does not cover.

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 December 2025 to March 2026 readings were taken more than six months before this count.

The airport record is complete. The Norristown record is not, and its comparison winters are uneven across the decades: 26 come from 1952-53 to 1984-85 and six from 2012-13 to 2022-23. The station’s daily readings end at a morning observation, while the airport’s day ends at midnight.

The count follows one definition. GLISA’s stricter definition gives lower numbers, 61 for the airport in 2025-26, and other researchers use others.

Asphalt roofing prices hit a record in August 2026, up 7.6% since April

Sat, 03 Oct 2026 15:51:10 -0400

The Bureau of Labor Statistics producer price index for prepared asphalt and tar roofing and siding products rose to 374.1 in August 2026, the highest reading in a series that starts in 1926. The index, which tracks what manufacturers receive for asphalt roofing products, was up 0.5% from July, 3.9% from August 2025 and 7.6% from April. The August figure was released on September 10 and is preliminary.

Asphalt roofing prices reached a record in August 2026

Producer Price Index, prepared asphalt and tar roofing and siding products, index 1982=100, not seasonally adjusted, monthly since January 2004

May through August 2026 can be revised. BLS revises producer price data for up to four months after first publication. Source: fred.stlouisfed.org

The index measures prices at the factory, before the distributor and the roofer. The Census Bureau’s definition of the industry behind these products, asphalt shingle and coating materials manufacturing, lists asphalt shingles, roofing felts, roofing cements and tar paper among what it makes.

Producer Price Index, prepared asphalt and tar roofing and siding products, the last 13 months. August 2026 is preliminary.
Month	Index (1982=100)	Change on month (%)	Change on year (%)
2025-08	360.038	0.2%	3.9%
2025-09	356.618	-0.9%	2.0%
2025-10	357.814	0.3%	-0.2%
2025-11	357.916	0.0%	1.4%
2025-12	354.925	-0.8%	0.7%
2026-01	347.005	-2.2%	-1.3%
2026-02	352.546	1.6%	1.2%
2026-03	346.394	-1.7%	-0.4%
2026-04	347.632	0.4%	0.8%
2026-05	354.678	2.0%	-0.9%
2026-06	367.585	3.6%	2.2%
2026-07	372.301	1.3%	3.6%
2026-08	374.098	0.5%	3.9%

Source: fred.stlouisfed.org

What moved

The rise started in May. The index climbed 2.0% that month, 3.6% in June, 1.3% in July and 0.5% in August. Before May it had drifted down, falling 2.2% in January and 1.7% in March, and in May it still stood 0.9% below its level a year earlier. By August the change on the year was 3.9%, the largest since August 2025.

Asphalt itself moved first. The industry definition describes these manufacturers as saturating mats and felts with asphalt from purchased asphaltic materials, and the BLS index for asphalt in its fuels and related products group jumped 32.9% from March to April 2026. It reached 326.5 in July, then fell 9.6% in August to 295.3, still 16.4% above August 2025. From March to August, the asphalt index rose 39.0% and the roofing index 8.0%.

Asphalt prices jumped in April 2026 and eased in August

Producer Price Index, asphalt, fuels and related products and power, index June 1985=100, not seasonally adjusted

Source: fred.stlouisfed.org

Read side by side, the two series show the roofing index rising a month after the asphalt jump. August’s 9.6% drop in asphalt did not show up in roofing prices, which rose 0.5% that month. If asphalt stays near its August level, the next few months of the roofing index will show whether the decline passes through. That is this site’s reading of the two series.

April to August across the years

The roofing index is not seasonally adjusted, so some of the April-to-August rise is the season. Prices for these products have risen from April to August in every year since 2015. Over the ten years from 2016 through 2025, the median April-to-August gain was 2.0%. Measured against each year’s April level, the index in June and July 2026 stood higher than in any year from 2015 through 2025.

The 7.6% gain in 2026 is the largest since 2021, when the index rose 8.7% over the same months. In the 22 years from 2005 through 2026, only 2008, 2011 and 2021 had larger April-to-August increases.

The April-to-August rise in 2026 was the largest since 2021

Percent change in the roofing index from April to August of each year, computed from BLS data

Source: fred.stlouisfed.org

What this means for a roof replacement

A roof replacement quote covers labor and scope as well as materials: the number of squares, the layers torn off, the sheathing, flashing and ventilation, as the guide to what moves the price of a roof replacement lays out. The materials line is the part that follows this index.

Ask how long a quote’s price holds, and for the materials line as a separate figure. A quote written in the spring and signed in late summer covers months when this index has risen every year since 2015.
Under Pennsylvania’s Home Improvement Consumer Protection Act, a contractor cannot depart from the agreed plans or specifications in any material way without a written change order, signed by both of you, that states the price change. See what a roofing contract has to include.
If a contract adjusts the price with a published index, the BLS guide to price adjustment clauses advises naming the index, the base and comparison months, and the date the calculation will be made, using the latest data published as of that date.

Caveats

These are national producer prices. They do not measure what a roofer pays a distributor or what an installed roof costs, and the index has no regional breakdown for southeastern Pennsylvania.

The index is not seasonally adjusted. That is why this article compares April to August across years instead of reading the 2026 rise on its own.

Producer price data are revised. The BLS guide says data are subject to monthly revisions for up to four months after first publication, so the values for May through August 2026 can still change. The next release, with September data, is scheduled for October 15, 2026.

The comparison between the asphalt index and the roofing index in this article is a comparison of their timing. It does not measure how much of the roofing index’s rise came from asphalt.