The center of a strong arctic high pressure moved through the Canadian prairies generating extreme cold conditions across northeast Montana with the combination of winds and frigid temperatures.  The event continued for all the zones into February 1st.

Extreme Cold/Wind Chill in SHERIDAN, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

At 2200 MST Medicine Lake RAWS and Comertown DOT had -40 wind chills for more than 2 hours.

Extreme Cold/Wind Chill in CENTRAL AND SE PHILLIPS, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

At 2245 MST had -40F or colder wind chills for several hours.

Extreme Cold/Wind Chill in CENTRAL AND SOUTHERN VALLEY, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

At 1753 MST several observation sites across the county had wind chill readings of -40F or colder for more than 2 hours.

Extreme Cold/Wind Chill in WESTERN ROOSEVELT, MONTANA
From 31-JAN-11 20:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

At 2200 MST several observation sites across Western Roosevelt county including the Wolf Point ASOS and McDonalds DOT had wind chills readings below -40F for more than 2 hours. This event continued into February 1st.

Extreme Cold/Wind Chill in EASTERN ROOSEVELT, MONTANA
From 31-JAN-11 20:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

At 2200 MST several observation sites including Poplar RAWS and Stateline DOT sensors recorded wind chills of -40F or lower for more than 2 hours.

Extreme Cold/Wind Chill in GARFIELD, MONTANA
From 31-JAN-11 20:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

At 2348 MST the Jordan ASOS reported wind chills of -40F or below for several hours.

Extreme Cold/Wind Chill in DANIELS, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

At 1700 MST Coronach Saskatchewan had wind chills at 40 below or lower for several hours overnight (this observation was used as no other was available in Daniels county).

Extreme Cold/Wind Chill in MCCONE, MONTANA
From 31-JAN-11 19:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

At 1900 the Cow Creek DOT station reported at least 2 hours of -40F or below wind chills that continued into the next day. At 1900 Fort Peck Handar also reported wind chills of -40F or colder.

Extreme Cold/Wind Chill in PRAIRIE, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

At 1800 MST, two observation sites in Prairie county had -40F or lower for more than 2 hours including Fallon and the Big Sheep RAWS.

Extreme Cold/Wind Chill in RICHLAND, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

At 2200 MST the Sidney AWOS had -40F or colder wind chills for several hours that lasted into February 1.

Extreme Cold/Wind Chill in DAWSON, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

At 1700, observations across the county had several hours of -40f or below wind chills including the AWOS at Glendive and Lindsay Divide DOT sensor.

Extreme Cold/Wind Chill in WIBAUX, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Beaver Hill DOT sensor had more than 2 hours of -40F or below that lasted into the next day.

Extreme Cold/Wind Chill in NORTHERN PHILLIPS, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

At 1855 MST Whitewater observation had -47F wind chill.

Extreme Cold/Wind Chill in NORTHERN VALLEY, MONTANA
From 31-JAN-11 17:00:00 to 31-JAN-11 23:59:00 (MST-7)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: RAWS

Bluff Creek RAWS had a windchill of -40 or colder beginning at 1844 MST that continued through the night. At 0500 10 miles south of Opheim, estimated -59 wind chill.