Commuters — those in vehicles and on foot — are finding treacherous conditions on the roads and sidewalks Tuesday morning after freezing rain and snow fell overnight across the metro and much of southern and eastern Minnesota.

Drivers who left their vehicles outside overnight are waking up to find windshields caked in ice, meaning a serious scraping session will be in order before hitting the roads.

Once on the go, expect things to be slow and slippery, especially on untreated side streets and sidewalks. That combination has led several metro area school districts to delay the start of classes.

The Minnesota Department of Transportation has 140 plows out across the metro dropping salt, said MnDOT spokesman Kevin Gutknecht.

“Keeping speeds down will be the key to driving success,” he said.

Lingering freezing rain “will cause travel difficulties and untreated surfaces will remain icy and contribute to hazardous travel through the morning,” the National Weather Service said.

By 5:50 a.m., the State Patrol had already responded to a number of spin outs and crashes, including a two vehicle wreck on the northbound I-35W bridge in Minneapolis and on westbound I-94 at 5th Street in Minneapolis.

The slick conditions have prompted several school districts to delay the start of classes by two hours. They include Burnsville, Rosemount-Apple Valley-Eagan, Shakopee, West St. Paul-Mendota Heights, Prior Lake, New Prague, Red Wing, Hope Christian in St. Paul Park and Bethany Academy in Bloomington. Some districts, such as Farmington, called off classes.

In the west metro, main roads like Hwy. 7, I-494 and I-394 in the Minnetonka and Hopkins area, were more slushy and sloppy than icy.

On Monday night, the State Patrol responded to a rash of crashes on Hwy. 52 near Rosemount. In one wreck, two SUV’s struck a jackknifed semitrailer truck that was blocking both southbound lanes near the Hwy. 55 interchange. No one was seriously hurt, said Lt. Tiffani Nielson of the State Patrol.

A winter weather advisory is in effect until 9 a.m., the weather service said. Light snow and drizzle is expected to taper off by midmorning. Then the sun should make an appearance with a high on Tuesday of 32 to 34 degrees.

Also in effect until midnight is an air quality alert. Fine particulate pollution has increased across the metro area and is approaching unhealthy levels for those with existing heart and lung conditions and for children and the elderly, the Minnesota Pollution Control Agency said.

The particles can exacerbate preexisting health conditions and cause chest pain, shortness of breath, wheezing, coughing or fatigue. Those sensitive to the conditions are encouraged to postpone or reduce vigorous activity and minimize exposure to local sources of air pollution, the agency said.