Ice storms, heavy snow and the winter roof calendar

What the database counts

NOAA's Storm Events Database follows the definitions in the National Weather Service's Storm Data instruction, and all three winter types below are entered by forecast zone:

• Ice storm: ice accretion that meets the local warning criteria, typically a quarter or half inch or more.
• Heavy snow: accumulation that meets local 12- or 24-hour warning criteria, with values such as 4, 6 or 8 inches in 12 hours depending on the area. The instruction notes that structural damage from the weight of snow may show up in the days after the snow ends.
• Winter storm: an event with more than one significant hazard, such as snow and ice, or heavy snow and blowing snow, where at least one element meets warning criteria.

Because entries are per zone, one broad storm can add dozens of events. Read each row for its shape, not as a count of storms.

Winter storm events by month, 2016-2025

The busiest month for each state is in bold.

Two patterns stand out. North of Iowa, the season is long: Minnesota, Wisconsin and Michigan each log well over 100 winter storm events in every month from December through April. From Kansas south, the season is short and lands mostly in January and February.

Ice storms: rare and concentrated

Ice storm counts are small, and a single year can make up most of a month. Of the 99 January ice storm events in Kansas, 80 came in January 2017 (one of them). Texas's 114 February events include 59 from February 2021 (example) and 44 from February 2023 (example).

Farther north, ice comes later in the winter. Michigan's ice storm events peak in February (52) and March (41), and Wisconsin's peak in March (28). Minnesota's cluster in December, with 29.

Colorado shows why ten years is a short record: all 75 of its September winter storm events came in September 2020 (one zone's entry).

Heavy snow and roof loads

Heavy snow peaks in December in Minnesota (302 events) and in February in Wisconsin (213) and Colorado (239), and Colorado logs heavy snow in every month from October through May. FEMA's Snow Load Safety Guide warns that temperatures swinging above and below freezing melt and refreeze snow into ice and ice dams, concentrating loads at the eaves of sloped roofs. The same guide recommends checking drains, gutters, downspouts and vents for snow or ice blockage before the next snowfall.

When to inspect, by region

Upper Midwest: after the last spring storm

Minnesota still logged 211 winter storm events in April, and Wisconsin 195. Book the post-winter inspection for May, once the April storms are past, and have it cover the roof edge, flashing and gutters.

Plains and Missouri: between the January peak and hail season

Iowa, Nebraska, Kansas and Missouri all peak in January. An inspection in February or early March catches winter damage before hail arrives; Missouri recorded 830 hail events in March over the same decade.

The South: after each event

Texas, Oklahoma, North Carolina, Georgia and Louisiana concentrate their winter storm events in January and February. There is no long season to wait out, so inspect after each ice or snow event instead of saving it for spring.

For damage you already have, the National Roofing Directory's roof repair guide explains the options, and you can find a roofer or follow active weather on the Storm Center. Spring hail timing is on the hail season page.

Frequently asked questions

When is ice storm season in Texas?

Mostly February. Texas logged 114 of its 161 ice storm events in February over 2016-2025, with most of them in 2021 and 2023, and smaller numbers in January and October.

What counts as an ice storm in NOAA's records?

The National Weather Service enters an ice storm when ice accretion meets locally defined warning criteria, typically a quarter or half inch or more. If freezing rain is mixed with other precipitation types, the event is logged as a winter storm instead.

Should I shovel snow off my roof?

FEMA's snow load guide cautions that removing all of the snow can damage the roof covering and recommends leaving at least 2 inches. It also advises plastic rather than metal shovels, no sharp tools such as picks, and staying clear of the eave when using a snow rake, since roof snow can slide at any moment.

When should I book a roof inspection after a Minnesota winter?

In May. Minnesota recorded 211 winter storm events in April over the decade and none in May, so a May inspection sees the roof after the season has finished with it.