When you wake up, you’ll want to put on shorts. But keep those wool socks handy.

An Indian summer and something forecasters are calling a “bomb cyclone” will collide Monday over much of the country, throwing the Douglas County area for a 43-degree temperature swing and leaving parts of the Great Lakes under feet of snow.

Lawrence will start its day with temperatures in the high 40s and will quickly warm up into the mid-60s by lunchtime, according to the National Weather Service. The balmy afternoon will top out at 68 around 4 p.m. But as the sun starts to go down, Mother Nature will flip the script.

The bomb cyclone and its blast of arctic air will begin to move in around 8 p.m., with temperatures dipping back into the 40s and then dropping precipitously. By midnight, the mercury will fall as low as 25, with 66 percent humidity and sustained winds of 25 mph that will make it feel much colder.

Tuesday will stay mostly in the 20s, with a few hours of 30-degree weather and sunshine in the afternoon.

That trend will continue the rest of the week — until Saturday, when it snows.