Cold wind chills Saturday could cause frostbite in as little as 30 minutes, according to a warning issued Friday by the National Weather Service.
A wind chill advisory is in effect from 5 a.m. to 1 p.m. Saturday in McHenry County, according to the warning.
Residents should expect wind chills to range from 15 degrees below zero to 20 below zero.
The extreme cold can cause frostbite or hypothermia unless precautions are taken, including wearing a hat and gloves.
National Weather Service meteorologist Charles Mott said residents also should expect this cold snap to last through at least next Friday.
“That’s as far as our forecasts go,” Mott said.