LOS ANGELES — Put away those shorts and tank tops, Chicago, and get ready for another “polar vortex.”

That’s what some people are calling the unseasonably cold temperatures expected to come to the Northern and Eastern United States next week, as a patch of cold air flows from northern Canada to the Great Lakes area and slips eastward toward the coast.

The temperature in some areas will slide as low as 15 to 20 degrees below normal, and some states are likely to see cold rain and thunderstorms as the air mass moves in, according to the National Weather Service.

The upper Midwest could see some of the coldest weather, with highs in the low- to mid-60s, and parts of the Chicago area could even see lows overnight dip into the 40s, forecasters say.

Residents as far south as Nashville could feel a 10-degree drop.

The cool air isn’t expected to be anything like the polar vortex of this January, which brought record-breaking subzero temperatures, school closures and wreaked havoc on air travel for weeks.

“I wouldn’t call it a polar vortex,” Mike Gillispie, a meteorologist for the National Weather Service in Sioux Falls, South Dakota, said of the latest temperature shift. “It’s going to be a shot of some colder air … but it’s not going to hang around for more than a few days.”

Still, some areas could flirt with record-low temperatures for July, said Andy Foster, meteorologist for the National Weather Service’s Central region.

The cool-down will bring little relief for the Western Seaboard, which will continue to sit in a ridge of high pressure that has sustained high temperatures and drought conditions for months.

In fact, the warm air mass parked on the West Coast is helping create a trough between Canada’s Hudson Bay and the Southwest, where the cold air will be flowing.