Cold/Wind Chill in Little Rocky Mountains, Montana

For multiple sites across the Little Rocky Mountains, temperatures in the teens to 30s below zero and breezy winds created intermittent periods of wind chills of 40 degrees below zero or colder from the evening of the 11th into the morning of the 15th. The peak wind chill of 58 degrees below zero was recorded at 8:00 AM, 7:15 PM to 7:30 PM on the 12th, and 12:00 AM to 12:15 AM on the 13th at the Hays MT-66 DOT site (MTHAY), at 7:41 AM on the 13th at the Manning Corral RAWS site (MCDM8), and at 2:00 PM and 8:30 PM on the 12th at the Malta South US-191 DOT site (MTMAL).

The coldest Arctic air mass in many years settled into the region with widespread temperatures of 20 to 40 degrees below zero and wind chills measuring between 40 and 70 degrees below zero.