Did Chicago not experience an Indian summer this year?
It appears Chicago skipped Indian summer in 2018, or did I just blink and miss it?
— Chuck Sebaski
“Indian summer” is a period of at least a few days of quiet, sunny, hazy and warm weather in the autumn that occurs after a frost or freeze. It is a “weather singularity,” a weather event that recurs (autumn, in this case) at about the same time of year. Indian summer occurs in the Midwest, Great Lakes region and northeastern portion of the United States.
We did not experience an Indian summer this past autumn. It is only an occasional visitor, occurring on average every few years. It happens when a large, sprawling high pressure system becomes stationary, or nearly so, over the eastern portion of the country. The associated weather is fair and dry, usually cool initially, then gradually warmer.