An initial Canadian cold front brought a much colder airmass southward through North-central Montana to nearly the I-90 corridor on the 11th. As a mid level warm front overran this airmass, instances of heavy snow were observed from the 12th into the 13th.
Every event with a place to put it; 8 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS TFX wrote it up.
An initial Canadian cold front brought a much colder airmass southward through North-central Montana to nearly the I-90 corridor on the 11th. As a mid level warm front overran this airmass, instances of heavy snow were observed from the 12th into the 13th. Cold air near the surface and warm nose aloft between the Helena area and Townsend area resulted in significant icing the morning of the 12th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Great Falls, MT wrote its last area forecast discussion before the first event at Dec 10, 4:48 PM MST, 13 hours 12 minutes earlier.
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</html>The national radar mosaic for the moment the first event began.
7 heavy snow, 1 ice storm. Local standard time, as filed.
Official NWS obs at the Havre Airport, in addition to multiple public reports, reported snow in excess of 6 inches. The peak report was from 15 N Rudyard and was 10 inches.
Trained spotter 5 NNE Loma reports 7 inches new snow in total by the report time. Snow was heavy at the time of the report but we never received a follow-up report with a final total.
A coop observer in Stanford and the public near Buffalo observed snow in excess of 6 inches, with the highest amount (8 inches) near Buffalo. Start time is estimated.
Multiple reports, including from trained spotters and coop observers, reported storm total snow in excess of 6 inches. The peak reports were from Lewistown as well as Grass Range, which were both at a foot.
Social media report of one quarter of an inch of ice accrual between Townsend and Deep Creek Pass.
A report from the public was received that stated 7 inches of snow fell in Chinook on the 12th. Start, criteria, and end times are all estimated.
A coop observer in Chinook measured storm total snow of 8.9 inches over two reports. The start, criteria, and end times are estimated.
Trained spotter 9 SW Chinook reported 8 inches new snow during the day on the 12th, ending at the report time. Start and criteria time are estimated.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2025Every state in 2025This day in weather historyWarnings in Montana, December 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 1300731, 1300726, 1300728, 1300730, 1300725, 1300732, 1300733, 1300724.