If you were standing on Michigan Avenue last fall, you probably felt it. That weird, lingering warmth that just wouldn't quit. Honestly, the weather in chicago in october 2025 felt more like a confused September than the crisp, sweater-weather intro to autumn we usually expect.
The numbers don't lie. National Weather Service data shows Chicago's mean average temperature for the month hit 58.1°F. That’s a whopping 4.1 degrees above what's considered "normal."
Most of us expect to be dodging lake-effect wind and freezing rain by Halloween. Instead, we got a month where the air stayed stubborn and soft. It was the kind of weather that makes you leave your jacket in the car and regret it only slightly once the sun dips behind the Willis Tower.
The Heat Wave Nobody Expected
The first few days of the month were basically a summer encore. On October 3, the mercury spiked to 88°F at O'Hare. The next day? It hit 87°F.
While that's not a record-shattering "hottest ever" moment—the all-time October record for Chicago is 94°F set back in 1946—it was enough to keep the patio season alive way past its expiration date. People were still ordering iced lattes and sitting outside at Big Star like it was the Fourth of July.
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But that warmth wasn't just a fluke. The average high for the month was 66.1°F. If you’re a native Chicagoan, you know that’s usually when we start panicking about the "Big Freeze," yet the freeze never really showed up in force.
Marathon Day: Perfect or Too Hot?
There’s always a huge debate around the Chicago Marathon weather. On Sunday, October 12, 2025, the conditions were technically "agreeable," but it depends on who you ask.
If you were a spectator at Mile 18, it was a dream. Sunny. Clear skies. Highs around 67°F.
However, for the runners in Wave 2 and Wave 3, the "sun blasting on your face" (as one runner put it on Reddit) turned the second half of the race into a bit of a slog. It was dry, sure, but that direct October sun is deceptive. The air was dawning in the low-to-mid 50s at the start, which is "PR territory" for elites, but as the humidity sat around 77% early on and the temps climbed, the event status actually shifted from green to yellow.
Basically, it was a "spectator's marathon" but a "runner's test."
Where Was the Rain?
Chicago is usually known for those gray, drizzly October days that feel like a noir film. Not in 2025.
We only saw 2.67 inches of liquid precipitation. That's nearly an inch below the historical average. It’s a trend we’ve been seeing lately—drier falls that leave the crunchy leaves just... sitting there. No soggy piles, just bone-dry sidewalks.
Interestingly, while places like Kentucky were getting absolutely hammered with record-breaking rain in early October, the Chicago "bubble" stayed relatively dry. We had plenty of "trace" days where you'd see a few drops on the windshield, but nothing that required the heavy-duty boots.
And snow? Forget about it. We recorded exactly 0.0 inches. While October snow isn't super common, a "trace" is the norm. In 2025, the flakes stayed home.
The Real Breakdown of Temperatures
It's easy to look at averages and miss the "feel" of the month. Here is how the mercury actually behaved across the 31 days:
The Early Surge (Oct 1–Oct 6)
Daytime highs stayed consistently in the 80s. This was the most anomalous part of the month. The low temperatures during this stretch were in the mid-60s—which is actually higher than the typical high for late October.
The Cooling Trend (Oct 7–Oct 20)
This is when reality started to set in. Highs dropped into the 60s and 70s. It was the sweet spot. If you had a wedding in Chicago during this window, you absolutely won the weather lottery.
The Late-Month Dip (Oct 21–Oct 31)
Finally, the "Windy City" teeth came out. On October 22, the high was only 50°F. By the 24th, we saw our lowest overnight dip of the month at 34°F. It didn't quite hit a hard freeze at O'Hare, but the suburbs definitely saw frost on the pumpkins.
Why 2025 Matters for the Future
Climate experts at the Midwestern Regional Climate Center noted that Illinois had its 9th warmest October on record in 2025. This isn't just a "nice month"; it’s part of a broader shift where the "growing season"—that time between the last frost of spring and the first freeze of fall—is stretching out.
We aren't seeing the sudden, violent shifts to winter as much as we used to. Instead, the shoulder seasons are blurring. September is becoming an extension of summer, and October is becoming the new September.
Planning for Next Time
If you’re looking at these 2025 patterns to plan for future October trips or events in Chicago, here’s the deal. Don't pack the heavy parka yet, but don't trust the 80-degree forecasts either.
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- Layers are the only law. The 30-degree swing between a 5:00 AM coffee run and a 2:00 PM walk in Millennium Park is real.
- Hydrate for the sun. The lower humidity in October makes you forget you're losing moisture. 2025 proved that even "cool" sun can cook you during a long run or hike.
- Watch the lake. Onshore winds kept the city slightly cooler than the inland suburbs during that early heatwave. If you want relief from the heat, head toward Navy Pier.
Basically, the weather in chicago in october 2025 taught us that the "Old Farmer's Almanac" rules are being rewritten. You can't just assume it’s going to be cold. Sometimes, the city just wants to stay warm a little longer.
If you are planning a visit for the coming year, keep a close eye on the Lake Michigan water temperatures. They act as a massive heat battery that keeps the city's overnight lows much higher than the surrounding prairie land, a phenomenon that was on full display throughout 2025.
Check the local NWS Chicago briefings about 72 hours out—they are far more accurate than any long-range app for catching those sudden cold fronts that "spin up out of nowhere," just like the one that saved (or scorched) the marathon runners this past year.