Strong Wind Risk in the US: How FEMA Scores It and How to Prepare
Most wind damage in America has nothing to do with tornadoes. Straight-line thunderstorm winds — downbursts, gust fronts, and the long-lived windstorms called derechos — damage far more property in a typical year than tornadoes do, simply because they cover vastly more ground. The August 2020 Midwest derecho drove 100+ mph winds across 770 miles of Iowa and Illinois and caused roughly $11 billion in damage — more than most hurricanes. In the National Risk Index, strong wind (hazard code SWND) accounts for roughly $3.2 billion in national expected annual loss across 3,121 counties.
What counts as strong wind risk
The NRI’s strong wind hazard covers damaging straight-line winds outside tornadoes and hurricanes, which the index books separately. The main actors: downbursts (rain-cooled air slamming down from a storm and spreading out at 60–100+ mph), derechos (a chain of downbursts riding a fast-moving storm line for hundreds of miles), and severe gust fronts. Damage looks like a tornado’s weaker cousin spread over a huge area — trees down everywhere, roofs stripped, power out for days, grain bins and signs flattened.
The signature consequence is the power outage: straight-line wind is the leading cause of large blackouts in the US, because a single derecho can drop thousands of trees onto lines across several states at once.
How the NRI measures it
FEMA combines each county’s exposure (building value and population), annualized frequency of severe wind events from NOAA storm reports, and historic loss ratios into an Expected Annual Loss, scored 0–100 relative to all counties. As with the other storm hazards, the ranking rewards places where frequent severe wind crosses dense development.
Where the risk concentrates
The current top five is more geographically scattered than most hazards: Monmouth County, NJ leads (score 100, ~$91M expected annual loss, nearly 6 severe-wind events/year — the Jersey Shore’s exposure to both thunderstorm winds and nor’easter gradients), followed by Jackson County, OK, Orange and Polk Counties, FL (Orlando/Lakeland — Florida’s daily-thunderstorm capital), and Ocean County, NJ. The broader high-risk zones are the derecho corridor from the upper Midwest through the Ohio Valley, the southern Plains, and the mid-Atlantic coast.
How to read your county’s score
A high strong-wind score mostly forecasts trees on things and days without power, punctuated by occasional structural damage to roofs and outbuildings. The relevant questions: What is the condition of the large trees within falling distance of your house and service line? How long can your household run without grid power — especially refrigerated medication, well pumps, or medical equipment? Is your roof covering rated and in good condition (wind peels shingles at the edges first)?
What actually reduces the risk
- Manage the trees. Professional pruning of large trees near the house, and removal of dead or diseased ones, prevents the single most common severe-wind loss. After any big blow, re-inspect — partially failed limbs come down in the next storm.
- Backup power, sized honestly. A portable generator (run outdoors, far from openings — carbon monoxide kills more people after windstorms than the wind does) or battery station covering the fridge, phones, and medical gear turns a week-long outage into an inconvenience. Whole-home standby units make sense where outages are routine.
- Harden the roof edge: ring-shank nails or added fastening on sheathing during a re-roof, sealed roof deck, and rated shingles — the same upgrades that resist hurricanes resist derechos.
- Anchor the light stuff. Trampolines, patio umbrellas, and sheds become projectiles at 70 mph; carports and grain bins need engineered anchoring.
- Treat severe thunderstorm warnings seriously. “Destructive” (80+ mph) severe thunderstorm warnings now trigger phone alerts; that’s tornado-grade wind arriving in minutes — get inside, away from windows, and don’t wait to see it.
The windstorms that made the case
The Midwest derecho of August 10, 2020 is the defining modern event. A single fast-moving storm complex crossed roughly 770 miles from South Dakota to Ohio in about 14 hours, producing winds well over 100 mph across central Iowa. It flattened millions of acres of corn, destroyed grain storage across the state, damaged a large share of the buildings and nearly all the mature trees in Cedar Rapids, and left hundreds of thousands without power for more than a week. Total damage ran to roughly $11 billion — more than most hurricanes that make landfall in the US — from a storm with no name, no forecast cone, and almost no national coverage while it was happening.
The June 2012 mid-Atlantic derecho ran from Indiana to the Atlantic in an afternoon and evening, hitting the Washington D.C. metro after dark with 80+ mph winds. Millions lost power during a severe heat wave, and the resulting heat deaths and communications failures — including 911 outages across northern Virginia — reframed derechos as a public-health and infrastructure problem rather than a tree problem.
The “Super Derecho” of May 2009 crossed Kansas and Missouri with embedded tornadoes and a rare, well-documented mesoscale vortex, and it advanced the meteorological understanding of how these systems sustain themselves for hundreds of miles.
Downburst research after Eastern Air Lines Flight 66 (1975) and Delta Flight 191 (1985) is the reason we understand this hazard at all. Tetsuya Fujita’s investigation of both crashes identified the microburst — a small, intense column of descending air producing a violent wind shift near the ground — and led directly to the airport terminal Doppler radar network and the wind shear training that has largely eliminated this class of aviation accident. The same phenomenon is what knocks down trees and strips roofs in an ordinary thunderstorm.
Season, timing, and where the corridor runs
- Peak season is May through August, with derechos overwhelmingly a warm-season phenomenon. The classic “derecho corridor” runs from the eastern Plains through Iowa, Missouri, Illinois, Indiana, and the Ohio Valley, with a second axis across the mid-Mississippi Valley into the mid-Atlantic.
- Late afternoon and evening dominate, though derechos frequently sustain themselves overnight — one of their more dangerous traits, since they arrive over sleeping communities with high-end wind and no visual warning.
- Florida and the Gulf Coast see the highest raw frequency of severe thunderstorm wind reports, from near-daily summer convection producing wet microbursts.
- The mid-Atlantic and Northeast coast add non-thunderstorm wind: nor’easter pressure gradients and post-frontal windstorms that produce sustained damaging wind for many hours rather than minutes.
- The interior West has its own varieties: high-wind events on the Front Range downslope of the Rockies, Great Basin gap winds, and the Columbia Gorge, all capable of 70–100 mph gusts with no thunderstorm at all.
The National Risk Index’s ranking follows severe-wind report frequency multiplied by what is underneath, which is why the top of the table mixes the Jersey Shore, central Florida, and the southern Plains rather than tracking any single meteorological pattern.
Hardening against wind, and the outage that follows
Straight-line wind damage concentrates in two places: what falls on your house, and the edges of your roof.
- Trees are the biggest single variable. A professional arborist’s assessment of large trees within falling distance of the house, the driveway, and the service drop is money well spent. Remove dead and diseased trees, thin dense crowns to let wind pass, and prune limbs overhanging the roof. After every significant windstorm, re-inspect: partially failed limbs and root-heaved trees come down in the next storm.
- Fasten the roof deck and the edges. Wind peels a roof from its perimeter inward. Re-nailing sheathing with ring-shank nails at closer spacing, installing a properly fastened drip edge, and sealing the deck seams are inexpensive during a re-roof and raise the failure threshold substantially — the same measures that resist hurricanes.
- Rated roof coverings. Shingles carry wind ratings; a 130 mph rated shingle installed with the correct nail pattern is a different product from the same shingle installed with four nails and no starter strip. Installation quality matters as much as the rating.
- Garage doors and large openings. A garage door that fails lets pressure into the building and can lift the roof from the inside. Wind-rated doors or brace kits are among the cheapest structural upgrades available.
- Anchor everything loose. Trampolines, patio furniture, umbrellas, empty trash bins, and unsecured sheds become projectiles at 70 mph. Carports, awnings, and grain bins need engineered anchoring, not intent.
- Consider FORTIFIED. The IBHS FORTIFIED roof standard was developed for hurricane wind but performs identically against derecho wind, and its Roof designation is achievable during any ordinary re-roof.
Plan for the outage, because that is the real consequence. Straight-line wind is the leading cause of large multi-day blackouts in the US, since one system can drop thousands of trees onto lines across several states simultaneously. Size backup power honestly around what actually matters: refrigerated medication, a well pump, medical equipment, phones, and the refrigerator. A portable generator or a large battery station covers most households; whole-home standby units make sense where multi-day outages are routine. Run generators outdoors only, well away from doors, windows, and vents — carbon monoxide poisoning kills more people after windstorms than the wind itself does. Keep a supply of water if you are on a well, since no power means no pump.
Insurance and claim mechanics
- Wind is a covered peril on standard homeowners policies, but check whether your policy applies a separate wind/hail deductible, often a percentage of the dwelling limit rather than a flat amount.
- Tree damage has specific rules. Most policies cover removal of a tree only when it has struck a covered structure, and typically with a low sublimit (often around $500–$1,000 per tree and a cap per event). A tree that falls in the yard and hits nothing is usually your problem. A neighbor’s tree falling on your house is normally your own policy’s claim, not theirs, absent proven negligence about a visibly dead tree.
- Food spoilage and power interruption are typically covered with a small sublimit, and only when the outage results from a covered on-premises loss in some policies. Read the terms before you throw out a freezer.
- Detached structures — sheds, fences, carports — carry their own percentage sublimit of the dwelling coverage, which is often far below replacement cost.
- Additional living expense applies if the house is uninhabitable, which after a multi-day outage in extreme heat or cold it may legitimately be. Ask.
- Document the wind event. Save the NWS warning and the storm reports for your county. Insurers distinguish wind damage from wear, and dated evidence of a severe wind event in your area settles most of those arguments.
Before, during, and after
Before. Trim the trees, secure the yard, and know how long your household can go without power. Enable Wireless Emergency Alerts — the NWS now issues “destructive” severe thunderstorm warnings for storms expected to produce 80+ mph winds or baseball hail, and those trigger a phone alert like a tornado warning does, precisely because derecho wind is tornado-grade over a much larger area. Keep flashlights, batteries, a battery or crank weather radio, and a charged power bank where you can find them in the dark.
During. Treat a severe thunderstorm warning mentioning 70+ mph winds exactly as you would a tornado warning: get to an interior room on the lowest floor, away from windows, and stay there. The damage footprint of a derecho is far larger than a tornado’s, so “it will probably miss us” is a worse bet here. Do not go outside to watch or to move things. If you are driving, pull over away from trees and power lines; high-profile vehicles blow over in this wind.
After. Assume every downed line is energized, and stay far away from lines tangled in trees or fences. Report outages to the utility rather than assuming someone else has. Chainsaw injuries and falls from ladders injure enormous numbers of people in the days after a windstorm — hire out the work on large or tensioned limbs, and never cut anything touching a wire. Photograph damage before cleanup, keep receipts for tarps and emergency repairs (insurers reimburse reasonable mitigation), and check on neighbors who depend on powered medical equipment. In heat or cold, a multi-day outage is itself a health emergency; relocate vulnerable household members early rather than waiting it out.