A roof ages in three ways that have nothing to do with hail: sun on hot days, water that freezes and thaws in small gaps, and heavy rain that tests every seam. NASA's POWER dataset gives the daily numbers behind all three, and we pulled ten years (2014 to 2023) for each of our 206 cities. The spread is large. A roof in McAllen sees 183 days a year at 90°F or higher. A roof in Denver sees 147 days a year when the temperature crosses freezing in both directions.
Where the stress comes from
The median city in our directory has 40 days a year at 90°F or higher, 65 freeze-thaw days, 42.2 inches of precipitation and 6.85 days with an inch of rain or more. A freeze-thaw day here means the daily low was below 32°F and the daily high above it. The chart below puts each city on both temperature axes. Hot cities tend to have few freeze-thaw days (correlation -0.54), so the two stresses mostly sit in different places.
Only one city, Rio Rancho, sits in the top quarter on both measures. Wichita, Kansas shows how a mid-country city carries a mix of everything: 65 hot days, 87 freeze-thaw days, 32.9 inches of precipitation and 6.0 heavy-rain days a year. A roof there faces sun, frost cycling and downpours in the same twelve months, and then hail on top.
The extremes, side by side
| City | Ranks high for | Days 90°F+ | Freeze-thaw days | Rain (in/yr) | Days 1 in+ rain |
|---|---|---|---|---|---|
| McAllen, TX | Hottest | 183 | 1 | 25.7 | 4.0 |
| Edinburg, TX | Hottest | 178 | 2 | 26.0 | 4.6 |
| Laredo, TX | Hottest | 176 | 4 | 20.0 | 2.7 |
| Brownsville, TX | Hottest | 145 | 1 | 25.4 | 5.0 |
| Denver, CO | Most freeze-thaw | 20 | 147 | 18.0 | 0.3 |
| Fort Collins, CO | Most freeze-thaw | 40 | 132 | 17.4 | 0.5 |
| Arvada, CO | Most freeze-thaw | 42 | 130 | 17.9 | 0.4 |
| Santa Fe, NM | Most freeze-thaw | 40 | 129 | 12.8 | 0.1 |
| Gulfport, MS | Heaviest rain | 66 | 11 | 70.1 | 15.5 |
| Biloxi, MS | Heaviest rain | 34 | 4 | 66.4 | 15.0 |
| Lake Charles, LA | Heaviest rain | 30 | 4 | 67.6 | 14.9 |
| Little Rock, AR | Heaviest rain | 84 | 51 | 57.8 | 14.5 |
The wettest city in the data, Gulfport, gets 70.1 inches of precipitation and 15.5 days of an inch or more each year. The driest, Las Cruces, gets 9.3 inches. Santa Fe counts 0.1 heavy-rain days a year, so rain there arrives rarely, though when it does a roof still needs to shed it.
Many hot days: heat bakes asphalt shingles, and a hot attic adds to it, so ventilation matters more. Ask a roofer what ventilation your attic has and what shingle rating the quote assumes.
Many freeze-thaw days: water that gets under shingles or flashing expands when it freezes, so pay attention to flashing, ice-dam protection at the eaves and gutters that drain.
Many heavy-rain days: underlayment, valleys, chimney flashing and gutter capacity do the work. A small leak shows up quickly in these places.
Each climate asks for a different check, so tell a contractor which one your city has and ask what they do about it.
Reading these numbers carefully
- A satellite-based grid, not a weather station. NASA POWER reports on a grid about 50 km across. A city with hills or a coastline can differ from the grid-cell average.
- Neighbors share a cell. Cities close together fall in the same grid cell and carry identical numbers. Fort Collins, Greeley and Loveland are one example, and the table lists such a group once.
- Ten years only. The window is 2014 to 2023, and individual years vary. Treat the figures as a typical year, not a forecast.
- This does not measure damage. A freeze-thaw day describes weather, and a roof's condition depends on materials, installation, ventilation and age. Hail is a separate story, covered in our guide to roof age and hail.
- Thresholds are fixed. We count 90°F as hot and 1 inch of rain as heavy everywhere, even though what counts as heavy differs by region.
Frequently Asked Questions
Which US cities are hardest on roofs?
It depends on what you count. In our 206 cities, McAllen has the most 90°F days (183), Denver the most freeze-thaw days (147) and Gulfport the most heavy-rain days (15.5).
What is a freeze-thaw day?
A day when the lowest temperature is below 32°F and the highest is above 32°F. Water can freeze at night, thaw in the afternoon and freeze again, which is the pattern that pushes at gaps in roofing.
Does a hot climate shorten the life of a roof?
Heat is one factor among several. Shingle type, ventilation, color and installation also matter, so ask a contractor about those rather than reading the climate alone.
Where do these weather figures come from?
From NASA POWER (MERRA-2 and IMERG reanalysis), daily values for 2014 to 2023 on a grid about 50 km across, averaged to a typical year.
Where the numbers come from
Data: climate values from city_facts for 206 cities, each from the grid cell nearest the city, yearly average over 10 years. Processed by PickARoofer.
Sources
- NASA POWER, daily point data (MERRA-2 / IMERG), 2014 to 2023 (power.larc.nasa.gov)
How we write and fund our articles: editorial policy.
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