How strong was the wind? Gusts, warnings and roof damage

The 58 mph line

The NWS counts a thunderstorm as severe when it produces winds of at least 58 mph, or 50 knots. That wind criterion did not change in 2010, when the hail line moved from penny to quarter size. Severe thunderstorm warnings can also carry a damage threat tag: considerable at 70 mph and destructive at 80 mph.

Reading the wind from what you see

Without a wind gauge of your own, you can estimate from what you saw. The NWS office in Burlington, Vermont, gives spotters a chart that ties wind speed to visible effects:

The same page marks 58 mph as the point where a thunderstorm is considered severe. If you saw trees down, you were likely in the second band or higher, which is why the roof checker treats downed trees as an inspection trigger.

The Enhanced Fujita scale and the roof

SPC implemented the Enhanced Fujita scale in the U.S. on February 1, 2007. It rates a tornado from 3-second gusts estimated at the point of damage, judged against 28 damage indicators. The bands run from EF0 at 65 to 85 mph up to EF5 at over 200 mph, with EF1 at 86 to 110, EF2 at 111 to 135, EF3 at 136 to 165 and EF4 at 166 to 200.

For houses, the indicator is one- or two-family residences. The Texas Tech recommendation that SPC hosts sets out its degrees of damage and expected wind speeds, and the first steps are all about the roof:

The lower bound for losing part of a roof covering in that table, 63 mph, sits just above the NWS severe line of 58 mph.

Hurricanes use a different scale

The National Hurricane Center rates hurricanes by sustained wind on the Saffir-Simpson scale. At Category 1, 74 to 95 mph, NHC says well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. By Category 3, from 111 mph, well-built framed homes may lose roof decking and gable ends.

Where to find measured gusts

• NWS local storm reports. A local storm report is an NWS text product that relays reports from spotters, local officials, media and the public, quality-controlled by the forecast office and preliminary until certified into Storm Data.
• SPC storm reports. Each day's page lists wind reports in mph with location and comments, all marked preliminary. The checker opens the right date for you, or start from the SPC reports index.
• NOAA's Storm Events Database. The long-term record is the Storm Events Database, where wind magnitudes are in knots and flagged as measured or estimated.

For scale, NOAA's Storm Events Database records 9,360 thunderstorm wind events in Pennsylvania and 9,262 in Texas from 2016 through 2025, counted by county, with Georgia at 8,679 and Virginia at 8,429. Damaging wind is not only a Plains problem.

After a high-wind storm

Start with NRD's storm damage roof repair guide, then read why roof claims get denied before you file. When you need a contractor, the find-a-roofer directory and the NRD Storm Center are the places to begin.

Frequently asked questions

Can a gust below 58 mph damage a roof?

It can. The EF-scale tables put the threshold of visible damage to a house at an expected 65 mph with a lower bound of 53 mph, which is why the checker suggests a professional look after strong gusts below severe.

What is the difference between a measured and an estimated gust?

A measured gust comes from an instrument; an estimated gust is judged from damage or observation. The Storm Events Database flags each wind value as measured or estimated, so check which kind you are reading.

Why do early reports differ from the final record?

SPC treats every report on its daily pages as preliminary, and NWS local storm reports stay preliminary until they are certified into Storm Data, so sizes and speeds can change.