(NewsNation) —  Michigan State Patrol’s 6th District Lt. Michelle Robinson warns of severe temperatures, saying snow isn’t the issue.

“It’s very difficult for road crews to be able to put salt down because the temperatures are so low that the salt isn’t working,” Robinson said.

Wind conditions and icy road conditions have also caused multiple injuries across the state, according to Robinson.

Grand Rapids troopers are investigating a head-on crash involving a semi and a postal vehicle. The driver of the postal truck has been taken to the hospital with serious injuries.