All Yellowstone National Park roads south of Mammoth Hot Springs were closed to public travel at 5 p.m. on Sunday, due to hazardous driving conditions and numerous weather-related traffic incidents including Yellowstone staff responding to more than 30 motor vehicle accidents, stranded vehicles, and slide-offs across various areas of the park.

The temporary closure allowed road crews time to safely clear snow and address icy conditions, but the nasty weather persisted into Monday as even the Big Horn Basin saw snow squalls. Additional heavy snow and high winds were forecast to continue through Monday evening, further impacting visibility and road safety.

Roads south of Mammoth Hot Springs remained closed at the time as road crews worked to reopen them, keeping the Yellowstone Road alerts online page busy with updates. Yellowstone's roads close to vehicles on Oct. 31, with the exception of the road between the North and Northeast entrances, which remains open year-round. The park reopens for over-snow travel (snowmobiles and snow coaches) around mid-December and closes this winter recreation season in mid-March. 

Road closures in late October are weather-dependent and can be moved up if hazardous conditions arise. While many roads are scheduled to close for the season on the first Monday in November, storms can create dangerous conditions that lead to temporary or permanent closures sooner.

According to Yellowstone National Park Lodges, winter in Yellowstone is characterized by cold and dry conditions. Daytime temperatures typically range from 0 degrees F to 20 degrees F and frequently fall below zero at night. Wind chill can make temperatures feel even colder — dangerously cold without recommended attire. Average annual snowfall in the park is 150 inches.

"You should always be prepared for sudden changes in the weather," the organization said.