INDIANAPOLIS (AP) – An arctic blast that sent temperatures below zero across most of Indiana also has brought dangerously cold wind chills to the state.

Thursday morning's frigid readings prompted numerous school closures and delays as districts sought to protect children from exposure to the dangerous cold.

The National Weather Service says temperatures by daybreak Thursday had fallen to between zero and minus 10 degrees across Indiana.

A wind chill advisory covers northern and central Indiana, while a wind chill warning covers the state's southern and southeastern counties. Wind chills are forecast to hover between 15 and 30 degrees below zero through Friday morning across Indiana.

The Indiana Department of Homeland Security is warning residents that sub-zero wind chills can lead to frostbite in 30 minutes or less.