Temperatures have significantly cooled down this week across Illinois, luring many residents into a false sense of hope that fall has finally arrived.
But despite the nearing return of the Pumpkin Spice Latte and the chillier evenings, temperatures are expected to heat back up again this weekend. This confusing phenomenon is sometimes referred to as a "false fall."
Here's what that means, and when Illinois residents can expect true autumn weather.
What is a 'false fall' and how does it impact the environment?
AccuWeather's lead long-range expert Paul Pastelok told USA TODAY that these early cool temperatures help signal to the trees that fall is coming, describing the phenomenon as "a long preview."
"Trees are very smart," he said, explaining that the shortening days are also a factor for the trees to change, but, "the weather can have a kind of a push on when these trees start to shut down. … Getting this week of cool weather, the trees start to notice that kind of stuff. You may start to see things start to shut down a little bit on and a little bit of less green tint in the green trees going forward here in the next week or so."
Climate change's impact on 'false fall'
Pastelok told USA TODAY the impacts of climate change can influence fall in different ways depending on the area. For example, in the Northwest, the above-80 temperatures last longer, throwing off the timing of the foliage. Some season changes also vary year by year, he said.
Climate change can also throw off other parts of the seasonal ecosystems like the migration patterns of insects and droughts, and cause severe weather, all of which can contribute to changing the foliage.
Story continues after photo gallery.
When will fall weather hit Illinois?
Fall officially begins Monday, Sept. 22, and the Old Farmer's Almanac says most of Illinois will likely experience a cooler-than-average season, barring northwestern regions near Iowa and Missouri.
Eastern Illinois will see average temperatures of 62 degrees in September, while southern and western Illinois will see average temperatures of 68 and 69 degrees, respectively.
Most of the state will experience scattered showers and warmer periods at the beginning of September before temperatures cool off at the end of the month.
Others are reading: Tired of hot weather? See what Old Farmer's Almanac, NOAA say about Illinois fall forecast
Meanwhile, the National Oceanic and Atmospheric Administration says the weather in Illinois will likely lean warmer than usual September through November, with temperatures expected to be in the top third of the climate record.
The administration finds that there's a 33-40% chance of the temperatures leaning warmer in the southern half of the state and a 40-50% chance in the northern half.
Kinsey Crowley contributed to this article.
This article originally appeared on Journal Star: What is a 'false fall'? See 2025 autumn forecast for Illinois
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