Temperatures are expected to drop near or below freezing overnight through the next few days.
The National Weather Service is putting a freeze warning in effect for large portions of Southern Arizona until 10 a.m. Friday.
Those cold temperatures mean drivers need to be aware of ice on the roadways, particularly on bridges.
They also need to wrap uninsulated water pipes and sensitive plants, and keep pets out of the cold.
“We have a section of Catalina Highway that is closed right now except for residents and employees,” said Priscilla Cornelio, director of the Pima County Department of Transportation. “And one of the reasons is we have our snow plows up there.”
All of the state is expected to see low temperatures in the 30s during the weekend, with portions of northern and eastern Arizona staying below freezing the entire weekend.
“The entire U.S. from the Front Range westward has been in what we call an upper trough,” said National Weather Service meteorologist Carl Cerniglia. “It’s just a big area of low pressure that seems to favor the western part of the U.S. recently.”
Temperatures will begin to warm up early in the week, but Cerniglia said as long as the trough stays over the west, low temperatures and precipitation are likely.