Measurements indicate that a slowly developing La Niña will affect winter conditions in most of the country. There’s a 60% chance of it emerging somewhere between September to November, with the expectation that it will continue through March,

When Chicagoans woke up to a sunny start to the week with a high temperature forecasted above 80 degrees — or as one meteorologist said, “definitely on the unseasonably warm side” — some might have hoped it’s a harbinger of a mild winter.