If you’ve lived in Prospect Heights for more than a week, you know the drill. You wake up to a crisp 35-degree morning, and by lunchtime, you’re wondering if you should’ve worn a t-shirt or if the sky is about to open up. It's fickle.
Honestly, the weather in Prospect Heights IL is a lot more than just "Chicago-adjacent" cold. We sit in a weird little pocket of Cook County where the proximity to Chicago Executive Airport and the Des Plaines River creates a micro-climate that can feel entirely different from downtown Chicago.
Why the Forecast Always Feels Off
Ever notice how O’Hare might be reporting light flurries, but here near Camp McDonald Road, you're getting slammed with three inches of heavy, wet slush? It isn't just bad luck.
Prospect Heights sits at a slightly different elevation than the lakefront. We lose that "lake effect" buffer that keeps the city warmer in the winter, meaning our nights are often five to seven degrees colder than the Loop.
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Weather in Prospect Heights IL and the "Airport Effect"
Since a huge chunk of our local data comes from Chicago Executive Airport (PWK), the numbers can be skewed. Large stretches of asphalt at the airport hold heat differently than the residential gardens over on Spruce Terrace.
Just last week, on January 8, 2026, we saw a bizarre spike in temperature that hit 60°F. Then, the rain hit. Hard.
The National Weather Service recorded flash flooding right here in the Wheeling and Prospect Heights area because of that unseasonable warmth. When you have record-breaking rain in the middle of winter, the frozen ground can’t absorb a drop. It just sits there. Basements in the north end of town were working overtime with sump pumps.
The Real Seasonal Breakdown
- Winter (December - March): It’s gray. January is statistically the cloudiest month, with overcast skies about 57% of the time. Average highs hover around 32°F, but the wind chill is the real killer.
- Spring (April - May): This is when things get messy. April is the wettest month on average. We're talking 3.49 inches of rain that turns backyard grass into a sponge.
- Summer (June - August): July is the peak. It hits an average high of 84°F, but the humidity can make it feel like 95°F.
- Fall (September - November): This is the sweet spot. September is arguably the best month to be outside, with highs in the mid-70s and way less humidity than August.
Surviving the Summer Humidity Spikes
Summer here isn't just about heat. It’s about that heavy, "soup-like" air.
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Being inland away from the lake, we don't always get that "lake breeze" that saves the city. If there's a heatwave, we feel the full brunt of it. It's the kind of weather where your AC unit becomes your best friend and your electricity bill becomes your worst enemy.
Experts like State Climatologist Trent Ford have noted that Illinois summers are getting wetter and more intense. We see fewer "all-day drizzles" and more "one-hour deluges" that overwhelm the storm drains.
Managing the Flooding Risks
Because we are nestled near the Des Plaines River watershed, flooding is the "silent" weather threat. You don't need a hurricane to see water in your street.
High-intensity storms are becoming more common. If you’re looking at property near the old Slough area or the lower-lying parts of the city, checking the drainage is more important than checking the roof.
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Practical Steps for Local Residents
Don't just trust the generic "Chicago" weather app. It's often wrong for our specific zip code.
Instead, look at the PWK (Chicago Executive Airport) station data specifically. It’s the most accurate reading for our immediate vicinity.
Next Steps for You:
- Audit your sump pump: If you haven't checked it since the January 2026 floods, do it now before the spring rains.
- Plant for the climate: Use native Illinois plants that can handle the 20-degree winter swings and the 90-degree summer humidity.
- Monitor PWK directly: Use the National Weather Service's specific page for Chicago Executive Airport to get real-time wind speeds, which are usually higher here than in the surrounding suburbs.