Johnston Weather Forecast: How Cold Will It Get Tonight?

Cold temperatures are expected overnight in Johnston into Tuesday morning with dangerous wind chills falling well below zero across Iowa -- into the zero to -15 range, says KCCI.com.

Lows in the Des Moines metro area will drop to near 1 degree overnight. The high on Tuesday will only be 15 degrees.

The National Weather Service has issued a wind chill advisory from 10 p.m. to 9 a.m. for parts of northern Iowa -- check county-by-county alerts here.

Wind chills are expected to drop quickly this evening to -20 by late evening in northern Iowa. Wind chills of -20 to -30 are expected by daybreak.

Those conditions mean frostbite can happen in as little as 15 to 30 minutes. When outside make sure you wear a hat and gloves.

The Weather Channel is calling for a low of 2 tonight in Johnston, followed by a high on Tuesday of 17 and an overnight low Tuesday of 11. The high on Wednesday should rebound to 30, but fall off again Thursday with a high of only 18.