Behind a strong cold front that brought a few inches of snow to northeast Montana the last week of December, northwesterly flow returned, bringing very cold weather and dangerous wind chills to the area beginning on New Year's Eve and lasting through January 2nd of the new year. Wind chills dropped to less than 50 below zero in a few locations.

Extreme Cold/Wind Chill in GARFIELD, MONTANA
From 01-JAN-18 07:00:00 to 01-JAN-18 07:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Temperatures were in the teens below zero much of the morning of the 1st. With easterly winds at 10 to 15 mph, wind chills were down into the 30s below zero across Garfield County, and a wind chill of 40 below was recorded at the Mesonet site near Sand Springs at 7 AM.

Extreme Cold/Wind Chill in SHERIDAN, MONTANA
From 01-JAN-18 17:45:00 to 02-JAN-18 03:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

With temperatures in the teens below zero and winds gusting above 30 mph at times, wind chills across portions of Sheridan County were less than 40 below zero for several hours on the evening of the 1st and into the early morning hours of the 2nd.

Extreme Cold/Wind Chill in WESTERN ROOSEVELT, MONTANA
From 01-JAN-18 03:18:00 to 01-JAN-18 08:18:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

With bitter cold temperatures dropping into the 30s below zero and easterly winds of approximately 10 mph, wind chills dropped into the 40s and even 50s below zero across western Roosevelt County, with the lowest wind chill recorded being 59 below zero at the Poplar RAWS at 8:18 AM MST.

Extreme Cold/Wind Chill in CENTRAL AND SOUTHERN VALLEY, MONTANA
From 01-JAN-18 00:53:00 to 01-JAN-18 06:53:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Bitter cold temperatures and relatively light easterly winds produced wind chills of less than 50 below zero early on the morning of the 1st across portions of Valley County. The coldest wind chill recorded in the county was at the Glasgow ASOS, which recorded a wind chill of 54 degrees below zero at 3:53 AM on January 1st. This event was a continuation from the evening of December 31st, when the Glasgow ASOS recorded a wind chill of 56 degrees below zero.

Extreme Cold/Wind Chill in MCCONE, MONTANA
From 01-JAN-18 17:37:00 to 01-JAN-18 22:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

With bitter cold temperatures and winds gusting to approximately 20 mph, wind chills were able to drop to less than 40 degrees below zero at a couple of locations across McCone County on the evening of the 1st. The lowest recorded wind chill was 46 degrees below zero at the Cow Creek DOT site.

Extreme Cold/Wind Chill in DAWSON, MONTANA
From 01-JAN-18 20:00:00 to 02-JAN-18 02:00:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Bitter cold temperatures and winds gusting to approximately 25 mph contributed to the production of extreme wind chill values of less than 40 degrees below zero over portions of Dawson County from the evening of the 1st into the early morning hours of the 2nd. The coldest wind chill recorded was 46 degrees below zero at 8:43 PM MST on the 1st.

Extreme Cold/Wind Chill in PRAIRIE, MONTANA
From 01-JAN-18 04:08:00 to 01-JAN-18 04:08:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Bitter cold temperatures and winds gusting to approximately 25 mph contributed to the production of wind chill values of less than 30 degrees below zero over portions of Prairie County on the 1st, and once dropped values to less than 40 below. The coldest wind chill recorded was 48 degrees below zero at 4:08 AM MST on the 1st, recorded at the Big Sheep Mountain RAWS.