When Mankato schools Supt. Ed Waltman checked the National Weather Service Web site at about 8:30 p.m. Wednesday night, he decided to make the call early so parents could plan.

What he saw was the possibility of air temperatures still hovering around 20 degrees below zero at noon Thursday. That’s without a wind chill factor.

He would have considered a two-hour delay, but the weather service was giving little hope things would be better before noon. The arctic air mass was expected to move in tonight and stay for awhile.

“It’s unusual to cancel school the night before,” he said. “But this isn’t like a storm where it might miss you.”

As of 9:30 p.m. tonight, public and private schools in Mankato, the Le Sueur-Henderson School District, Janesville-Waldorf-Pemberton, Minnesota Valley Lutheran in New Ulm and Waterville-Elysian-Morristown were planning to close for the day tomorrow. St. Clair was set for a two-hour late start, but warning that updates were possible.

Other school districts set for a two-hour delayed start were: Blue Earth Area, Butterfield-Odin, Lafayette, Lake Crystal Wellcome Memorial, Madelia, Maple River, Martin County West, Mountain Lake, Nicollet, New Ulm, St. James, Truman and United South Central.