As chilly air takes hold in areas from Denver to Minneapolis and Chicago, much cooler air will expand to areas from Dallas to Atlanta and New York City in the coming days.
The chilliest air since last spring will continue to advance southward and eastward over the United States to end the week. Some areas of the Rockies and Plains will also have the first snow of the season.
Temperatures were hovering in the 30s over much of Montana with snow falling in some locations, including Cut Bank and Lewistown, on Wednesday.
Snowflakes are forecast to fall around Denver with a coating possible in the foothills and areas north of the metro area during Thursday night into Friday.
The outbreak will bring a freeze to portions of the northern High Plains and the risk of frost to areas farther to the east and south over the northern and central Plains.
According to AccuWeather Senior Meteorologist Dale Mohler, "While a freeze will not reach areas where major crops have not reached maturity, scattered frost will be a concern for backyard gardens over the North Central states."
Temperatures will dip into the 40s around Chicago with some of the chilliest suburbs reaching the upper 30s this weekend.
As the cold air continues to push southward, snow will fall over portions of Wyoming, western South Dakota, the Nebraska Panhandle and parts of Colorado.
According to AccuWeather Senior Meteorologist Kristina Pydynowski, "Rapid City, South Dakota, will shatter their coldest daytime high of 49 F on Thursday, with a high temperature forecast to only reach the upper 30s."
The record on Wednesday at Rapid City was set in 1950.
"The coldest daytime high for the entire month of September is 34 F," Pydynowski said.
At the peak of the chilly air outbreak, temperatures over the Plains will average 20 to 30 degrees below normal.
The air mass will reach into Texas as well.
High temperatures in Dallas during the first 10 days of the month have been in the 90s. In the wake of the front, temperatures will be slashed by 20 to 30 degrees by Friday. Temperatures will be no higher than the 70s on Saturday.
The much cooler air will reach Houston and San Antonio, Texas, as well.
Cool air, without snow, will push eastward and will reach the Appalachians and Atlantic coast by this weekend. While the cool air in the East will not be record-shattering, it will make it feel like autumn.
Nighttime temperatures will dip into the 50s from Boston to New York City and Washington, D.C. Temperatures in the northern and western suburbs of these cities will dip into the 40s.
There is a chance of scattered frost in the coldest spots of northern Pennsylvania, upstate New York and northern New England by early next week.
While it will take some time, temperatures will trend downward in the Deep South as the cooler air continues to sprawl.
After many days with highs in the 90s, high temperatures in Florida Peninsula locations, such as Orlando, are forecast be in the 80s during the middle and latter part of next week.
An area will the chilly air will not reach is west of the Continental Divide. Most areas west of the Rockies to the Pacific coast will continue to experience near- to above-average temperatures into next week.