The rules behind the storm roof checker, and their sources

The four inputs

1. Largest hail seen or reported: none, pea, penny, quarter, half dollar, ping pong ball, golf ball, hen egg, tennis ball, baseball or softball.
2. Strongest wind: none noticed, strong gusts below severe, 58 mph or more measured or in a severe thunderstorm warning, trees or large limbs down nearby, or a tornado or damage path nearby.
3. What you can see from the ground: missing or lifted shingles, tiles or panels; dents in gutters, downspouts, vents or AC fins; granules piling at downspouts; a tree or limb on the roof; water stains or drips inside; loose flashing or metal.
4. Roof type. The four results come from hail, wind and visible damage, so roof type does not change which one you get.

The hail sizes follow the object comparisons on the Storm Prediction Center's hail size table: penny 0.75 inch, quarter 1.00, half dollar 1.25, ping pong ball 1.50, golf ball 1.75, hen egg 2.00, tennis ball 2.50, baseball 2.75 and softball 4.00. SPC's table starts at marble size, so the pea, at 1/4 inch, comes from NWS office charts such as the Baltimore/Washington office's SKYWARN chart.

Rule 1: active damage comes first

Answer: Protect first, then book a repair. If you tick water stains or drips inside, or a tree or limb on the roof, the checker stops here. These are not signs that damage might exist; the roof is already letting weather in or carrying a load it was not built for, so the useful next step is limiting the damage and getting a repair booked.

Rule 2: severe weather or a visible sign

Answer: Book a roof inspection. Any one of these triggers it:

• Hail 1 inch or larger. The NWS counts hail of at least 1 inch in diameter as severe thunderstorm criteria.
• Wind of 58 mph or more, measured or inside a severe thunderstorm warning. That is the NWS severe wind line, 50 knots, and a warning is issued when radar indicates a severe storm or a spotter reports 1-inch hail or 58 mph winds.
• Trees or large limbs down nearby. On the NWS Burlington spotter chart, winds of 55 to 72 mph push over shallow-rooted trees and damage chimneys and TV antennas.
• A tornado or damage path nearby. The lowest rating on the Enhanced Fujita scale, EF0, covers 3-second gusts of 65 to 85 mph.
• Any visible damage sign from the ground list, apart from the two that trigger Rule 1.

Rule 3: the near misses

Answer: A professional look is worth it. Two conditions lead here.

Penny-size hail, at 3/4 inch, was the NWS minimum for severe thunderstorm warnings until January 5, 2010, when every forecast office moved to 1 inch. The same notice left the 58 mph wind criterion unchanged.

Strong gusts below severe are the other trigger. The Texas Tech damage tables that SPC hosts put the threshold of visible damage to a house at an expected 65 mph, with a lower bound of 53 mph, so a gust just under the warning line can still leave marks.

Rule 4: nothing above

Answer: Probably fine — do a ground check. This covers no hail or pea-size hail, no notable wind and nothing visible. A daylight walk around the house, and a second look after the next heavy rain, is the whole job.

Why order matters

The rules run from top to bottom and stop at the first match. A single dented downspout therefore outranks pea-size hail, and a drip on the ceiling outranks everything, even if the storm itself never reached severe levels.

The storm report link

The checker writes the SPC link in the form spc.noaa.gov/climo/reports/YYMMDD_rpts.html for the date you pick; the page for June 2, 2024, for example, is 240602_rpts.html. SPC says each page covers reports received from 1200 UTC to 1159 UTC the next day, with data back to June 1, 1999. On those pages, hail is logged in hundredths of an inch and wind in mph, and all reports are considered preliminary.

Final numbers come later. NWS local storm reports remain preliminary until they are certified locally and nationally and entered into NWS Storm Data, and NOAA's long-term record is the Storm Events Database.

The state links

Choose a state and the checker also links that state's pages on the National Roofing Directory: its storm center page and its find-a-roofer page. The national starting points are the NRD Storm Center and the find-a-roofer directory.

What the rules leave out

The checker cannot see your roof, and hail size and gust speed are stand-ins for what actually hit it. It is also no substitute for warnings while a storm is under way: NWS safety advice is to go to a small interior room on the lowest floor and stay away from windows when severe thunderstorms threaten.

Frequently asked questions

Why is penny-size hail not an automatic inspection?

Because the current NWS severe threshold is 1 inch. Penny size was the old warning threshold, so the checker treats it as worth a closer look rather than a definite inspection.

Does my roof type change the answer?

No. The four answers depend on hail, wind and what you can see; roof type is collected alongside them.

Where do the fallen-tree and tornado rules come from?

The fallen-tree rule uses the NWS Burlington wind estimation chart for spotters, and the tornado rule uses the EF-scale thresholds published by SPC.