Ice Storm Risk in the US: How FEMA Scores It and How to Prepare

Written by Dvir · Data: FEMA National Risk Index v1.20 · Updated August 4, 2026

Of all winter precipitation, freezing rain is the most destructive per inch. Half an inch of ice adds hundreds of pounds to tree limbs and power lines; an inch can bring down transmission towers. The result is winter’s signature disaster: the multi-day, sometimes multi-week blackout in freezing temperatures. The 1998 Northeast ice storm left millions without power for up to a month; the 2009 Kentucky storm and the 2021 Texas–South event followed the same script. In the National Risk Index, ice storms (hazard code ISTM) account for roughly $1 billion in national expected annual loss across 3,000 counties.

What counts as ice storm risk

An ice storm is freezing rain — rain that falls as liquid through a warm layer aloft, then freezes on contact with sub-freezing surfaces, glazing everything in solid ice. It is distinct from sleet (which bounces) and snow, and the NRI scores it separately from both winter weather and cold waves.

The damage chain is characteristic: ice accretes on trees and power infrastructure → limbs and lines fail together → outages last far longer than wind-caused ones because every span must be physically rebuilt while roads remain skating rinks. Casualties come less from the ice than from its aftermath: carbon-monoxide poisoning from generators and improvised heating is the leading killer after major ice storms, followed by falls, car crashes, and hypothermia in unheated homes.

How the NRI measures it

FEMA combines each county’s exposure (population and building value), annualized freezing-rain frequency from NOAA records, and historic loss ratios into an Expected Annual Loss scored 0–100 relative to all counties. The frequency data traces a surprisingly specific geography — the “ice belt” where warm Gulf air routinely overruns shallow cold layers.

Where the risk concentrates

The heart of US ice-storm risk is not New England but the Ark-La-Tex and the mid-South. The current top five: Caddo Parish, LA (Shreveport — score 100, ~1.5 ice storms/year), Red River County, TX, and three Arkansas counties — Pulaski (Little Rock), Benton (northwest Arkansas), and Sevier. The belt runs from northeast Texas across Arkansas, southern Missouri, Kentucky, and Tennessee, with a second corridor through the Appalachians and interior Northeast into upstate New York and northern New England. These are regions where heavy tree canopy, above-ground power lines, and recurring freezing-rain setups coincide.

How to read your county’s score

A high ice-storm score is essentially a forecast of extended winter power outages. The questions that matter: How long can your household keep warm, fed, and medicated without grid power in freezing weather? What hangs over your service line and driveway (ice-laden limbs fail exactly where they’re aimed)? Do you have safe backup heat — and working CO detectors? Rural areas on long distribution lines should plan for restoration measured in weeks, not days, after a major glaze event.

What actually reduces the risk

  • Backup power with CO discipline. A generator (run outdoors, 20+ feet from openings, never in a garage) or battery bank sized for heat circulation, refrigeration, and communications is the core mitigation. CO detectors on every level — after every major ice storm, CO deaths outnumber all other causes.
  • Tree work before winter: remove dead limbs and anything overhanging the roof, driveway, or your service drop. Utilities trim the mains; the line to your house is usually your exposure.
  • Stay off the roads during glaze. Freezing rain is the most dangerous driving surface that exists — even four-wheel drive has zero advantage on wet ice. Most ice-storm injuries are crashes and falls; bridges freeze first.
  • Prepare the house for cold without power: know your main water shutoff (pipes burst when heat fails), keep faucets dripping, close off rooms, and have sleeping bags rated below freezing as the last-ditch layer.
  • Charge everything and fill the tank when freezing rain is forecast — gas pumps and cell towers fail with the grid. A corded phone or battery radio still works when cell service saturates.

The ice storms that defined the hazard

The North American ice storm of January 1998 is the benchmark. Days of freezing rain across northern New York, Vermont, Maine, and eastern Canada accumulated three inches of ice in places, collapsing steel transmission towers, snapping tens of thousands of distribution poles, and destroying vast areas of forest. Millions lost power, some for a full month, in temperatures well below freezing. The death toll came overwhelmingly from hypothermia and carbon monoxide poisoning rather than from the storm itself. It permanently changed how utilities in the region design and stockpile for ice loading, and it is why every serious ice-storm plan starts with “assume weeks.”

Kentucky, January 2009. An ice storm across the mid-South left more than half a million customers without power in Kentucky alone, some for weeks, and produced the largest National Guard call-up in the state’s history. Rural distribution lines through heavy tree canopy are the worst case for restoration, because each mile has to be rebuilt by hand on iced roads.

Oklahoma and the southern Plains, December 2007 and again in October 2020. The October 2020 event was notable for hitting while trees were still in leaf — the extra surface area collected far more ice, and urban canopy damage in Oklahoma City was catastrophic. Early-season and late-season glaze events do disproportionate tree damage for exactly this reason.

Texas, February 2021. Winter Storm Uri combined ice, extreme cold, and a near-total failure of the state’s electricity generation and gas supply. Hundreds of people died, mostly from hypothermia in unheated homes and from carbon monoxide poisoning as families burned charcoal indoors and ran cars in garages for warmth. It is the clearest demonstration in modern American history that the deadly part of this hazard is the loss of heat, not the ice.

The physics, the ice belt, and the season

Freezing rain requires a specific and fairly common vertical structure: a shallow layer of sub-freezing air at the surface beneath a deeper layer of above-freezing air aloft. Snow falling from above melts completely in the warm layer, then supercools in the cold layer near the ground and freezes instantly on contact with anything at or below 32°F. If the cold layer is deeper, the drops refreeze in the air and fall as sleet, which bounces and is far less destructive. The difference between a nuisance and a disaster is often a few hundred feet of atmospheric depth.

  • Season is December through March, with a secondary risk in late autumn and early spring when trees still hold leaves and collect much more ice.
  • The primary ice belt runs from northeast Texas and Louisiana through Arkansas, southern Missouri, western Tennessee, and Kentucky — where shallow Arctic air pushing south is routinely overrun by warm, moist Gulf air aloft. This is the highest-frequency freezing-rain region in the country, and it is not New England.
  • A second corridor runs through the Appalachians, the interior mid-Atlantic, upstate New York, and northern New England, where cold air damming against the mountains produces the same setup.
  • The Pacific Northwest has a localized version in the Columbia River Gorge and the Willamette Valley, where cold air drains west through gaps beneath milder marine air.

Accumulation thresholds matter. A quarter inch of ice starts breaking small branches and makes every surface treacherous. Half an inch brings down large limbs and distribution lines. An inch or more collapses whole trees, snaps poles, and can bring down transmission structures — the multi-week outage scenario.

Hardening for the outage

Ice-storm mitigation is almost entirely about surviving days to weeks without grid power in freezing temperatures.

  • Backup power, sized for heat circulation. Most homes with gas or oil heat need only a few hundred watts to run the furnace blower and controls — a modest generator or a large battery station keeps the house warm. Have a transfer switch or a properly rated inlet installed by an electrician; back-feeding through a dryer outlet endangers line crews and is illegal in most places.
  • Carbon monoxide discipline is the difference between inconvenience and death. Run generators outdoors only, at least 20 feet from doors, windows, and vents, never in a garage even with the door open. Never heat with a charcoal grill, camp stove, unvented kerosene heater, or gas oven. Install CO detectors on every level and test them at the start of winter. After every major ice storm, CO poisoning is the leading cause of death.
  • Safe secondary heat. A wood stove or fireplace with a clean, inspected chimney; a properly vented propane heater rated for indoor use; or simply the ability to close off and occupy one small room. Sleeping bags rated below freezing are the last-ditch layer and are cheap.
  • Tree work before winter. Remove dead and diseased limbs, and anything overhanging the roof, driveway, or your service drop — the line from the pole to your house is typically the homeowner’s responsibility, and it is exactly what falling limbs are aimed at. Utilities trim the main lines; nobody trims yours.
  • Protect the plumbing for a no-heat scenario. Know where the main shutoff is, insulate exposed pipes, and if the house will be cold for days, shut off and drain the system rather than hoping. Burst pipes on the thaw are the most common property loss after long ice outages.
  • Stock for a week minimum, two if rural. Water (freezing well pumps stop when power does), non-perishable food that needs no cooking, medications, pet supplies, and cash. Fill the vehicle’s tank and charge everything when freezing rain is in the forecast — gas pumps, ATMs, and eventually cell towers all fail with the grid.
  • A battery or crank radio and a corded phone. Cell networks saturate and then their backup batteries run out. NOAA Weather Radio works when nothing else does.

Insurance and the claim pattern

  • Ice damage to the structure is generally covered by standard homeowners insurance: weight of ice bringing down a roof, a tree falling on the house, water entering through storm-created openings.
  • Tree removal has tight sublimits. Coverage typically applies only when the tree strikes an insured structure, often capped at a few hundred to a thousand dollars per tree. A yard full of destroyed trees is usually an uninsured expense — and after a major ice storm, tree services are booked for months and priced accordingly.
  • Frozen pipe bursts are covered when you maintained reasonable heat. Losing heat because the grid failed is a covered circumstance; leaving the house unheated and unattended without draining it usually is not. Document when the power went out.
  • Food spoilage carries a small sublimit and sometimes requires the outage to originate on your property, which a downed utility line does not. Read the terms before discarding a freezer’s contents — and photograph it first.
  • Additional living expense covers a hotel if the house is genuinely uninhabitable. A house at 35°F with no prospect of heat qualifies; call the insurer and ask rather than assuming.
  • Generators and space heaters purchased during the emergency are sometimes reimbursable as reasonable mitigation. Keep receipts.

Before, during, and after

Before. Take an ice storm warning as seriously as a blizzard warning — it means damaging freezing rain is expected. A winter storm warning mentioning freezing rain, or a freezing rain advisory, means lighter but still hazardous glaze. When the forecast shows a quarter inch or more of accretion, act as though the power will go out: charge everything, fill the tank and water containers, move vehicles out from under trees, and locate the flashlights and CO detectors.

During. Do not drive. Freezing rain produces the single most dangerous road surface that exists, and four-wheel drive provides no advantage whatsoever on wet ice — it helps you accelerate into a crash you cannot brake out of. Bridges and overpasses glaze first. Walking is nearly as hazardous: falls on glazed steps and driveways are a leading injury, and ice cleats over boots are a genuinely effective five-dollar intervention. Stay away from trees and lines while ice is falling and while it is thawing — limbs release unpredictably, and downed lines under ice may still be energized.

After. Assume every downed wire is live, and never touch a limb that is touching a wire. Report the outage rather than assuming a neighbor did. Check on people who live alone, especially anyone elderly or dependent on powered medical equipment; hypothermia indoors develops slowly and the person affected often does not recognize it. If restoration is measured in days and you cannot keep a room above roughly 55°F, leave for a shelter or a friend’s house — this is not a test of endurance. Photograph damage before cleanup, keep receipts for emergency expenses, and expect tree and roofing contractors to be overwhelmed for weeks.

Sources

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