Snow moved into western Oklahoma late Sunday afternoon and spread east over the rest of the state through the night.
The snow is expected to mix with or change to sleet and possibly light freezing rain after midnight, the weather service reported.
Cimarron and Texas counties in the Panhandle are the only Oklahoma counties excluded from the winter weather advisory, which expires noon Monday in western and central Oklahoma and 6 p.m. in eastern parts of the state.
Widespread snow accumulations are expected to average 2 inches or less. Snow and sleet are expected to end Monday, and will turn into rain, meteorologists said. Some counties across southern Oklahoma could see a few tenths of an inch of ice before temperatures rise above freezing Monday
“When we wake up, we may be dealing with some light freezing drizzle. I think by mid-morning, we'll see this pushing off into eastern Oklahoma. About that time we'll see temperature above freezing, so we'll start melting off a lot of the ice and snow that might be out there,” Ty Judd, meteorologist at the National Weather Service in Norman said.
Temperatures are expected to be in the upper 20s Monday night, so some refreezing is possible, Judd said. The rest of the snow and ice should be gone by sundown Tuesday.
“We're actually going to warm up this week. On Tuesday, it'll be back up into the 50s,” he said.
At 3 p.m., Oklahoma Highway Patrol troopers reported heavy snowfall from the Texas state line east to Elk City. By 5 p.m., roads in Beaver, Ellis, and Woodward counties were snow-covered and slick, troopers said. Freezing rain and light snow also were reported in Harper and Texas counties.
By 5 p.m., four inches of snow in Roger Mills County was reported to the National Weather Service. Roger Mills County sheriff's dispatcher Chris Clift said emergency responders had to help motorists as their vehicles slid off area roadways. At least two people were hurt in an accident, he said.
Four inches of snow was also reported near Cordell in Washita County. In Clinton, three inches of snow was reported and snowfall of two inches or more was reported at Altus, Elk City, Helena, Hobart, Hollis and Seiling, according to the weather service.
Snow began falling in Oklahoma City just before 9 p.m. The roads were wet, then started becoming slick about 10:30 p.m., according to police and fire radio traffic. Multiple wrecks were reported around the city, but no streets were reported closed.