Why so warm for so long? Stretch of unseasonable weather in metro Detroit

Posted at 11:18 AM, Sep 20, 2017
and last updated 2017-09-20 14:20:03-04

The autumn equinox arrives Friday and ushers in the beginning of fall, but it seems no one told Mother Nature. Starting Wednesday, we begin a stretch of unseasonably warm weather that lasts through the weekend and into next week. So why are we warming up at a time of year when we should be cooling off? It all has to due with the position of the jet stream, a fast moving current of upper level winds.

A disturbance out west associated with a pocket of cooler air is helping to funnel unseasonably warm conditions into the Plains and Great Lakes. This will lead to temperatures running 10-15 degrees above average for this time of year. The image below shows a jet streak (the fastest moving winds within the jet stream) over the Panhandles of Texas and Oklahoma.

The ridge of warming weather remains locked in place for Metro Detroit through this weekend and into next week. Notice the wind barbs out of the south bringing the warmer temperatures into the area. To the east Tropical Storm Jose continues to weaken, while Hurricane Maria moves north off the the coast.

The cooler conditions remain out west, but inch a little close Monday into Tuesday. Temperatures locally remain well above average in the middle 80s.

By the end of next week, a developing low moving to our north will allow cooler weather to pour into Metro Detroit, putting an end to the stretch of summer warmth.


October will represent a robust return to fall like temperatures. Jackets, sweatshirts and coat will be needed once again.

Between today's warmth, and the week-plus of mid-summer 80s, we could come close to a few record high temperatures. During this run of unseasonable temperatures to end September, record highs range from 87-93 degrees.

September 30 the record high drops to 85 degrees, coinciding with the return of cooler temperatures.