The cold weather makes fighting fires especially difficult.
Janesville Fire Shift Commander Bill Ruchti says their top priority is personnel. At some fires, crews will rotate to make sure firefighters stay warm. They bring out heaters to keep the plumbing on the engines and firefighters warm. Ruchti says the hoses are also full of water, so instead of shutting them off, firefighters have to leave the water running through the hoses. If they shut the hoses off in this weather, the line freezes and the hoses are worthless.
Officials say one of the top causes of fires in cold weather is heating appliances that haven't been used all season.
Scroll down to hear more about how firefighters keep warm in extreme weather.