Helena's cold snap is reaching dangerous temperatures, which were expected to plummet to negative 15 degrees Fahrenheit, with much colder wind chills by Tuesday morning. 

The National Weather Service reported the temperature in Helena will reach negative 15 degrees at 7 a.m. Tuesday, and wild chills in the area could be as low as 30 to 35 degrees below zero. Helena's all-time record low for Feb. 20 is negative 19 degrees, which was set in 1986. 

Central and southern Lewis and Clark County, along with the northern and southern Rocky Mountain Front, will remain under a wind chill advisory until noon Tuesday. 

Bob Hoenisch, meteorologist at the Great Falls National Weather Service, warns that it only takes 20-30 minutes for frostbite to set in at negative 20 to negative 30 degrees. And if it drops to negative 40, it only takes 10 minutes.

“Avoid going outside unless you have to,” he said. 

Hoenisch said the cold temperatures are not hitting just Helena, but will be spread over the entire state.

“There’s a cold air mass on top of us,” Hoenisch said, adding that the warmest areas are near Missoula. 

Independent Record Editor Jesse Chaney contributed to this report.