A large arctic air mass descended southward from Canada to spread across our region for multiple days.  Re-enforcing cold low pressure disturbances continued to rotate along the edge of this air mass, which supported this prolonged dangerously cold period. For most of these days, enough wind was present to create dangerously cold wind chill values for may locations across northeast Montana, and persisted through New Year's Eve.

Cold/Wind Chill in RICHLAND, MONTANA
From 27-DEC-21 05:21:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

For multiple sites across Richland County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from early morning of the 27th into the late night of the 31st. The peak wind chill of -45 was recorded at 10:16 PM on the 31st at the Badger Creek CWOP Mesonet site (MTMCD).

Cold/Wind Chill in DAWSON, MONTANA
From 26-DEC-21 23:03:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

At the Lindsay Divide DOT site (MTLND), temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from late night on the 26th into the late night of the 31st. The peak wind chill of -45 was recorded from 12:53 AM to 1:08 AM on the 27th.

Cold/Wind Chill in WIBAUX, MONTANA
From 26-DEC-21 23:08:00 to 31-DEC-21 21:55:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

For multiple sites across and near Wibaux County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from late night on the 26th into the night of the 31st. The peak wind chill of -43 was recorded at 7:35 AM on the 27th at the Beach, ND ASOS site (K20U).

Cold/Wind Chill in DANIELS, MONTANA
From 26-DEC-21 23:35:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across Daniels County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from late night of the 26th into the late night of the 31st. The peak wind chill of -52 was recorded at 5:13 AM on the 31st at the Navajo MT-5 DOT site (MTRED).

Cold/Wind Chill in CENTRAL AND SE PHILLIPS, MONTANA
From 27-DEC-21 01:15:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across Central and Southeast Phillips County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from the early morning of the 27th into the late night of the 31st. The peak wind chill of -49 was recorded at 3:20 AM on the 28th at the Saco US-2 DOT site (MTSCO).

Cold/Wind Chill in MCCONE, MONTANA
From 27-DEC-21 00:50:00 to 31-DEC-21 09:39:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across McCone County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from early morning of the 27th into the night of the 31st. The peak wind chill of -47 was recorded at 6:50 AM on the 27th at the Fort Peck Dam site (GGWFP).

Cold/Wind Chill in NORTHERN VALLEY, MONTANA
From 27-DEC-21 03:44:00 to 31-DEC-21 22:44:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

At the Bluff Creek RAWS site (BLUM8), temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from the early morning of the 27th into the late night of the 31st. The peak wind chill of -45 was recorded at 7:44 AM on the 27th.

Cold/Wind Chill in SHERIDAN, MONTANA
From 27-DEC-21 01:01:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across Sheridan County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse beginning as early as the morning of the 27th and lasting as long as the late night of the 31st. The peak wind chill of -53 was recorded at 9:34am on the 31st at the Comertown Turn-OFF MT-5 DOT site (MTCOM) as well as at 7:35pm on the 31st at the Sher-wood Airport (Plentywood) ASOS.

Cold/Wind Chill in CENTRAL AND SOUTHERN VALLEY, MONTANA
From 26-DEC-21 21:20:00 to 31-DEC-21 15:40:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

For multiple sites across Central and Southern Valley County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from late night of the 26th into the night of the 31st. The peak wind chill of -50 was recorded from 7:20 AM to 7:30 AM on the 27th at the Saint Marie MARCO site (07MT).

Cold/Wind Chill in WESTERN ROOSEVELT, MONTANA
From 26-DEC-21 00:45:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across Western Roosevelt County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from early morning of the 26th into the late night of the 31st. The peak wind chill of -50 was recorded at 11:01 PM on the 29th at the McDonald's MT-13 DOT site (MTMCD).

Cold/Wind Chill in EASTERN ROOSEVELT, MONTANA
From 27-DEC-21 06:03:00 to 31-DEC-21 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

For multiple sites across Eastern Roosevelt County, temperatures in the teens and 20s below zero and breezy winds created intermittent periods of wind chills of -40 or worse from the morning of the 27th into the late night of the 31st. The peak wind chill of -44 was recorded at 9:53 PM on the 31st at the US-2 Stateline DOT site (MTSTA).