Bundle up.

It’s bitterly cold again Tuesday morning in the Twin Cities and much of central and southern Minnesota, with windchills between 20 below and 30 below, and air temperatures in the single digits and teens below zero.

On Wednesday morning, it will be even colder, the National Weather Service said, with temperatures around 7 or 8 below at sunrise. But lo and behold, the air will warm into the teens Wednesday afternoon and into the 20s Thursday and Friday before another cold front descends Saturday.

The Weather Service issued a windchill advisory for Monday night into Tuesday. Northwest winds between 5 and 15 miles per hour will send windchills into dangerous territory, with the coldest readings between 6 and 9 a.m.

By 7 p.m. Monday, neither Minneapolis nor St. Paul schools had said they would cancel classes because of the cold.

The bitter cold prompted the Weather Service to issue a reminder that frostbite and hypothermia “can occur if precautions are not taken.” It also said frostbite can set happen in as little as 30 minutes.

The Minnesota Department of Transportation warned drivers that a coating of snow that fell Monday afternoon and evening could contribute to black ice and slick roads for the Tuesday morning commute. MnDOT’s message: Slow down.

Rock salt, normally used on roads, is less effective below 15 degrees, so roads are treated with liquid calcium chloride, which lowers the freezing temperature of the brine and prevents precipitation from bonding to the road surface.