Cold Wave 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

The most expensive cold-weather disaster in US history didn’t happen in Minnesota. It happened in Texas, in February 2021, when Winter Storm Uri held the state below freezing for days, collapsed the power grid, killed more than 200 people, and burst enough pipes to generate over $20 billion in insured losses. That event is the modern template for cold-wave risk: extreme cold is most dangerous where it is least expected. In the National Risk Index, cold waves (hazard code CWAV) account for roughly $9.9 billion in national expected annual loss — one of the largest hazards in the index — across 3,077 counties.

What counts as cold wave risk

The NRI’s cold wave hazard covers prolonged spells of dangerously low temperatures relative to what a region is built for — as distinct from winter weather (snow and blizzards) and ice storms, which the index tracks separately. Like heat, cold kills against a local baseline: -10°F is a normal Fargo commute and a statewide emergency in Houston, where homes have uninsulated pipes, heat pumps without backup strips, and no snow fleet exists.

The casualty mechanics are consistent: hypothermia among the homeless, elderly people in underheated homes, and people stranded in vehicles; carbon-monoxide poisoning from improvised indoor heating (generators, charcoal, ovens); and house fires from space heaters. The property loss is dominated by frozen and burst pipes — a single burst supply line can do tens of thousands of dollars of damage.

How the NRI measures it

FEMA combines each county’s exposure (population and building value), annualized cold-wave frequency from NOAA records, and historic loss ratios into an Expected Annual Loss scored 0–100 against all counties. Population-dense counties with real-but-occasional severe cold rank highest — the index is pricing people and property against how unusual the cold is, not against absolute temperature.

Where the risk concentrates

The top of the ranking pairs big-city exposure with serious cold: Cook County, IL (Chicago) leads with a score of 100 and a remarkable ~$700 million expected annual loss, followed by Milwaukee County, WI (~$177M). Then comes the Texas signature: Harris (Houston), Dallas, and Hidalgo (Rio Grande Valley) counties all sit in the national top five — enormous populations in housing never designed for hard freezes. High ratings blanket the Upper Midwest, Great Plains, and Northeast, but the Gulf South’s presence near the top is the risk map’s most important lesson.

How to read your county’s score

If you’re in the traditional cold belt, a high score mostly means the index is pricing your huge exposure — your housing and infrastructure are adapted, and preparation is routine. If you’re in a southern high-scoring county, take it as the Uri warning: your home probably has vulnerable plumbing, your heat probably depends on a grid that struggles in deep cold, and your community has thin cold-response capacity. The key questions: Where are your water pipes routed (attic and exterior-wall pipes are the burst risk)? What happens to your heat in a multi-day outage? Who do you know that lives alone and old?

What actually reduces the risk

  • Protect the pipes: insulate exposed runs, seal crawl-space vents in freezes, drip faucets on exterior walls during hard cold, and — most important — know where your main shutoff is so a burst is a mess, not a flood. Leaving for the holidays? Keep heat at 55°F+ or shut off and drain.
  • Heat safely or not at all. Space heaters need 3 feet of clearance and a hard surface; never heat with an oven, charcoal, or an indoor generator. CO detectors on every level are non-negotiable in outage-prone cold country.
  • Have a no-grid heat plan: a safe backup source (wood stove, vented propane heater rated for indoor use, or a generator run outdoors), or a pre-decided warm destination. Layered clothing and closing off one room stretches whatever heat you have.
  • Winterize the vehicle and carry a kit (blankets, water, snacks, phone charger, shovel) — stranding deaths cluster on rural highways in cold snaps.
  • Check on vulnerable people daily during warnings — the same intervention that saves lives in heat waves saves them in cold.

The cold waves that exposed the gaps

Winter Storm Uri, February 2021. Texas stayed below freezing for days. Natural gas wellheads and pipelines froze, generation tripped offline, and the ERCOT grid came within minutes of an uncontrolled collapse that would have taken weeks to restore. Rolling blackouts became multi-day outages in freezing homes. More than 200 people died — the state’s official tally, and independent analyses put it higher — overwhelmingly from hypothermia indoors and from carbon monoxide poisoning as families ran generators in garages, burned charcoal inside, and idled cars for heat. Insured losses from burst pipes alone exceeded $20 billion, making it the costliest winter event in US history. Its lesson is structural: cold-wave catastrophe is a grid and building-stock problem, not a temperature problem.

The January 2014 polar vortex pushed Arctic air deep into the Midwest, South, and East, breaking century-old records and freezing infrastructure in cities that rarely see single digits. It introduced “polar vortex” into everyday vocabulary and prompted a round of winterization requirements for power generators in several regional grids — requirements Texas notably did not adopt before 2021.

The Great Blizzard and cold outbreaks of the late 19th century, particularly the Schoolhouse Blizzard of January 1888, killed hundreds of people across the Plains, many of them children walking home from school, when a mild morning turned to −40°F conditions within hours. It is the origin of the American emphasis on cold-weather warning rather than mere forecasting.

Chicago, January 2019. A polar vortex intrusion brought wind chills near −50°F to the upper Midwest. The city’s response — mass shelter openings, transit warming buses, proactive wellness checks on the elderly and unsheltered — held the death toll far below what the temperatures alone would suggest, and stands as the counter-example to Texas 2021: the same physics, a prepared system, a very different outcome.

Season, geography, and the adaptation gap

  • Season runs December through February in most of the country, with the most dangerous events in January. Early-season cold in November and late-season cold in March do disproportionate damage because heating systems have not been serviced and pipes have not been protected.
  • The polar vortex mechanism. A strong, stable stratospheric polar vortex keeps Arctic air bottled near the pole. When it weakens or displaces — a sudden stratospheric warming event — lobes of extreme cold spill south into North America, typically with one to three weeks of lead time visible to forecasters. This is why cold outbreaks in the Midwest and South are increasingly forecastable well in advance.
  • The northern tier is adapted. Minnesota, the Dakotas, upstate New York, and northern New England experience far colder temperatures with far lower per-capita loss, because buildings are insulated, pipes are routed inside conditioned space, heating systems are sized for it, and the population knows what to do.
  • The Gulf South, Southwest, and Pacific Northwest carry the adaptation gap. Homes in Texas, Louisiana, Mississippi, Arizona, and coastal Oregon and Washington routinely have water lines in attics, exterior walls, and unconditioned crawlspaces; heat pumps without adequate backup heat; no insulation to speak of; and grids not winterized for sustained cold. The National Risk Index’s high ratings for Houston, Dallas, and the Rio Grande Valley are the single most important thing on this hazard’s map.
  • Wind chill is what injures people. At −20°F with a 20 mph wind, exposed skin can freeze in under 30 minutes; at colder combinations, in minutes. The NWS issues Extreme Cold Warnings (formerly wind chill warnings) on those thresholds, which vary by region precisely because acclimatization varies.

Protecting the building and the people

Pipes are the property loss. A single burst half-inch supply line can discharge hundreds of gallons an hour into a house nobody is standing in.

  • Find and label your main water shutoff now, and make sure everyone in the household can operate it in the dark. This is the highest-value five minutes of preparation for this hazard.
  • Insulate every pipe in unconditioned space — attic, crawlspace, garage, exterior walls. Foam sleeves are cheap; heat tape (UL-listed, installed to instructions) is the answer for the worst runs.
  • Seal the air leaks near plumbing. Cold air blowing across a pipe through a crawlspace vent or a gap around a sill plate freezes it long before ambient temperature would. Closing foundation vents during hard freezes is standard practice in the South.
  • Drip the faucets on exterior walls during a hard freeze — a moving trickle resists freezing and relieves the pressure that actually bursts the pipe. Open cabinet doors under sinks to let room heat reach the lines.
  • Disconnect and drain hose bibs, irrigation systems, and pool equipment before the season.
  • Leaving for a week or more? Either keep the thermostat at 55°F or higher, or shut off the water at the main and drain the system. The unheated, unattended house is the classic denied claim and the classic catastrophic loss.
  • Insulate the attic. In southern housing stock this is often the single largest improvement available, and it helps in summer too.

Heat safely. Space heaters need three feet of clearance from anything combustible, a hard flat surface, and a direct wall outlet — never an extension cord or power strip. Never heat with an oven, a charcoal or gas grill, a camp stove, or an unvented kerosene heater indoors. Run generators outdoors only, at least 20 feet from any opening. Install carbon monoxide detectors on every level and test them at the start of winter — in Texas in 2021, CO poisoning sent thousands to emergency rooms.

Have a no-grid plan. Decide in advance where you go if the heat fails for more than a few hours in hard freeze: a friend’s house, a warming center, a hotel. Closing off one interior room, layering clothing, and using below-freezing-rated sleeping bags buys time; it is not a multi-day solution. Households with infants, elderly members, or anyone on powered medical equipment should leave early rather than late.

Insurance and assistance

  • Frozen pipe damage is covered by standard homeowners insurance — with the near-universal condition that you maintained heat in the building or shut off and drained the water. Losing heat because the utility failed is a covered circumstance; document the outage times.
  • The claim volume overwhelms adjusters. After Uri, mitigation companies and plumbers were booked for months. Photograph everything, keep receipts for emergency water extraction and drying (insurers reimburse reasonable mitigation), and start the claim immediately.
  • Mold follows fast. Water from a burst pipe behind a wall causes mold within days. Aggressive drying in the first 48 hours is what keeps a plumbing claim from becoming a remediation claim, and mold coverage is often sublimited.
  • Freeze damage to outdoor plumbing, sprinklers, and pools is commonly excluded, as is damage from your own failure to maintain the system.
  • Food spoilage and additional living expense apply as in other outage events — ask about ALE if the house is genuinely uninhabitable.
  • LIHEAP funds heating bills, emergency furnace repair, and in some states weatherization for income-qualified households. Many states also prohibit winter utility disconnection during declared cold emergencies. Find out your state’s rule before you need it.
  • Vehicles. Comprehensive auto coverage handles a cracked block from a frozen cooling system; check your antifreeze concentration before the season rather than after.

Before, during, and after

Before. Know the alert vocabulary: a Cold Weather Advisory means seasonably dangerous cold; an Extreme Cold Watch means dangerous cold is possible in the next few days; an Extreme Cold Warning means life-threatening cold is expected or occurring. Thresholds differ by region because what is dangerous differs by region. When a warning is issued, do the pipe protection, charge everything, fill the vehicle, and confirm your plan for anyone vulnerable.

During. Check on isolated older people every day — indoor hypothermia is slow, the person affected typically does not recognize it, and it is the most common way cold kills in a home. Watch for the signs: shivering that stops, confusion, slurred speech, drowsiness, cold skin. That is a 911 call; warm the person’s core gradually with blankets and warm (not hot) drinks if they are conscious, and do not rub extremities. Frostbite shows as white or grayish, waxy, numb skin, usually on fingers, toes, nose, and ears — get indoors, rewarm in warm not hot water, and do not rub or use direct heat.

Bring pets indoors. Avoid travel; if you must, carry blankets, water, food, a charger, and a shovel, and tell someone your route. If stranded, stay with the vehicle, run the engine sparingly, and keep the exhaust pipe clear of snow.

After. Check the whole house for leaks as things thaw — a pipe that burst while frozen only floods when it warms. Shut the main and call a plumber at the first sign of water. Reset and test CO detectors. Check on neighbors again during the thaw, since heating costs and repair bills arrive right after the emergency and are their own kind of hardship.

Sources

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