The wind chill drove recess indoors at schools in Bismarck and Mandan.

"We have not been outside today because the wind chill is 15 below zero," St. Mary's Grade School Principal Gwyn Marback said.

Thursday, the wind chill was 20 below zero, and the temperature was 2 below, according to the National Weather Service. Today, the high is forecast at 2 below with a wind chill forecast between 19 below and 29 below.

Wind chill is the combination of what the temperature feels like and the wind speed. Lower temperatures combined with higher wind speeds decreases the amount of time it takes to get frostbite.

School policies follow the same guidelines. If the wind chill is 15 below zero or colder, outdoor recess is replaced with time indoors. The temperature without wind chill needs to be 10 below for outdoor recess to be cancelled. This is the general guideline Bismarck Public Schools, Mandan Public Schools, the Bismarck Catholic schools and Shiloh Christian School follow. Some schools, like Shiloh, have room for flexibility.

"If it's really cold, we don't go out," Shiloh elementary principal Ross Reinhiller said. Teachers have discretion. He's also found the students can handle the colder temperatures better than the adults supervising recess, he said.

Today's temperatures, combined with wind speeds, would give exposed skin a half hour before getting frostbite, according to a wind chill chart at the Centers for Disease Control. The CDC recommends people stay indoors and make short trips outdoors if needed. Dressing warmly also is recommended. This includes a hat, a scarf to cover the face, sleeves that fit snug at the wrist, mittens, water resistant coat and boots and several layers of loose fitting clothing, according to the CDC.

(Reach reporter Sara Kincaid at 250-8251 or sara.kincaid@;bismarcktribune.com.)