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