You’ve seen the memes. One day in central Illinois, it’s basically summer, and the next, you’re digging your car out of a snowbank. People joke about the "four seasons in one day" thing, but honestly, in Decatur, it’s not really a joke—it’s just Tuesday.
Right now, if you step outside in Decatur, you’re feeling a crisp 23°F. But that’s the "official" number. The real story is that 12°F feels-like temperature hitting your face thanks to an 11 mph wind coming off the southwest. It’s cloudy, it’s grey, and it’s very much January in the Soy Capital of the World.
The Immediate Outlook: Cold is an Understatement
If you’re looking at the Decatur Illinois weather forecast for the next 24 hours, grab the heavy coat. Seriously. Today’s high is maxing out at 23°F, but we’re looking at a low of 8°F tonight. There’s about a 25% chance of some light snow during the day, dropping slightly to 16% overnight.
Tomorrow, January 19, is going to be a "bright but brutal" kind of day. We’re expecting sun, which sounds nice, but the high is only hitting 13°F. With a low of 6°F and 18 mph winds from the west, that sunshine is going to be purely decorative.
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Actually, the National Weather Service in Lincoln has already issued a Cold Weather Advisory starting at 3:00 AM Monday through noon. If you’ve got pipes that like to freeze, tonight is the night to let them drip.
The 10-Day Rollercoaster
Looking further out, we get a tiny bit of relief before winter reminds us who’s boss.
- Tuesday (Jan 20): A "balmy" 32°F under partly sunny skies.
- Wednesday (Jan 21): The peak of our mini-thaw at 38°F.
- Late Week: Temperatures start sliding back down into the 20s.
- Next Weekend (Jan 24-25): This is the one to watch. We’re looking at highs in the teens (16°F Saturday, 9°F Sunday) with a much higher chance of actual snow showers—around 35%.
Why Decatur Weather is So Weirdly Aggressive
Geographically, Decatur is basically a playground for competing air masses. You’ve got the cold, dry Arctic air pushing down from Canada and the warm, moist air trying to creep up from the Gulf of Mexico. When they meet over the flat cornfields of Macon County, things get loud.
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Most people don't realize that December and January are historically some of our cloudiest months. In fact, data from the Illinois State Water Survey shows that December is the cloudiest month of the year here, with the sky being overcast about 55% of the time.
And let's talk about the wind. Because there aren't many hills to stop it, those "breezes" off Lake Decatur or the open fields can turn a cold day into a dangerous one. We're currently seeing southwest winds, but as that clipper system moves through, they’ll shift west and kick up to 18-20 mph.
The Severe Side of Things
Wait, did you know Decatur just had a tornado outbreak in December? On December 28, 2025, an EF2 tornado ripped through the Elwin-Mt. Zion area with peak winds of 120 mph. It stayed on the ground for over 23 miles. People think of tornadoes as a "spring thing," but in Illinois, if the humidity spikes and a cold front slams into it, the calendar doesn't matter.
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Dealing with the Dryness
Humidity is currently sitting at 52%. That might sound okay, but in the winter, that’s "static shock every time you touch a doorknob" territory. It’s expected to climb toward 74% by next Sunday when the snow chances increase, but for now, the air is dry and biting.
What You Should Actually Do
- Check your tires. Cold air makes tire pressure drop. If your light isn't on yet, it probably will be by Monday morning when it hits 6°F.
- Layers, obviously. But specifically, wind-blocking layers. A 13 mph wind at these temperatures isn't just uncomfortable; it's a frostbite risk if you're out for more than 30 minutes.
- Watch the Saturday/Sunday window. If you have travel plans for the 24th or 25th, the 35% snow chance combined with single-digit highs suggests some slick, packed-down ice on I-72 and Route 51.
Winter in central Illinois is basically a test of endurance. We’re currently in the thick of the "cold season," which historically lasts until about March 1. The average high this time of year is usually around 35°F, so staying in the 20s and teens means we are well below the seasonal norm. Stay warm, keep the salt bucket handy, and maybe just stay inside on Monday.