Imperial County reached the benchmark maximum for extreme-heat days.
Imperial County, California recorded 1,204 county-days at or above 100°F and one freeze day during 2016–2025.
View Imperial County →Roof Year · Data & Press
Data journalists can use.
Roof Year is a fixed 2016–2025 benchmark of historical weather exposure across 3,144 U.S. counties and county equivalents. It brings together six measures from public NOAA and NASA datasets, with 2025 Census county geometry. The figures describe county-level exposure—not the condition of any individual property or roof.
See Roof Year →Citation
Free to cite with attribution.
- Recommended citation
- Source: RoofClearly Roof Year, 2016–2025 U.S. county benchmark
- Preferred linked attribution
- RoofClearly Roof Year — https://roofclearly.com/roof-year/
- Publication-ready source line
- Source: RoofClearly analysis of NOAA GHCN-Daily, NOAA Storm Events and NASA POWER data, 2016–2025.
Please link attribution to the main Roof Year page.
Headline findings
Six views of one national benchmark
North Slope Borough reached the benchmark maximum for freeze days.
North Slope Borough, Alaska recorded 2,762 county-days at or below 32°F, the highest valid freeze total in the frozen benchmark.
View North Slope Borough →Pennington County set both frozen hail benchmarks.
Pennington County, South Dakota recorded 130 reported county-days with hail at least 1 inch and 34 with hail at least 2 inches—the maximum for each measure in this benchmark.
View Pennington County →Tooele County reached the benchmark maximum for severe-wind days.
Tooele County, Utah recorded 139 reported county-days with thunderstorm wind of at least 50 knots.
View Tooele County →Yuma County reached the benchmark maximum for cumulative solar exposure.
Yuma County, Arizona recorded 21.65 MWh/m² of cumulative all-sky surface shortwave irradiation during 2016–2025.
View Yuma County →The same decade produced sharply different county profiles.
Maricopa County recorded 1,095 extreme-heat days and 19 freeze days; Pennington County recorded zero extreme-heat days and 1,756 freeze days.
Compare Maricopa and Pennington →Use the work
Explore, compare or download
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- Explore the weather map →
- Compare counties →
- Check my roof history →
- Download the benchmark CSV →
Frozen 2016–2025 benchmark · 3,144 counties and county equivalents · six exposure measures · county GEOID included. Blank temperature values mean insufficient valid NOAA coverage; they are not zero.
Methodology
Methods in brief
Benchmark. January 1, 2016 through December 31, 2025, covering 3,144 U.S. counties and county equivalents.
Extreme heat. County-days with a daily maximum temperature of 100°F or higher, from NOAA GHCN-Daily with coverage quality control.
Freeze. County-days with a daily minimum temperature of 32°F or lower, from NOAA GHCN-Daily with coverage quality control.
Hail ≥1 inch. Distinct county-days with at least one NOAA Storm Events report of hail 1 inch or larger.
Hail ≥2 inches. Distinct county-days with at least one NOAA Storm Events report of hail 2 inches or larger.
Severe wind. Distinct county-days with reported thunderstorm wind of 50 knots or more in NOAA Storm Events.
Solar exposure. Cumulative NASA POWER ALLSKY_SFC_SW_DWN all-sky surface shortwave irradiation, expressed in MWh/m². It is irradiation, not roof temperature.
Geometry. U.S. Census TIGER/Line 2025 county geometry supports the map.
Storm Events reporting practices and hail thresholds changed around 2010. Temperature values that do not pass coverage QC remain blank rather than being shown as zero.
Read the detailed methods →Limitations
What the benchmark cannot show
Historical county exposure only. Roof Year does not determine whether a specific roof was struck, damaged, degraded, how much life remains, or when replacement is needed.
Roof Year does not produce a combined score.
Contact
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