Weather in Chicago

Midwesterners have a saying about the weather: "If you don't like it, wait five minutes." Chicago earns it. You get all four seasons here, sometimes in a single April afternoon, and while summers usually run hot and muggy and winters cold and gray, there's plenty of swing inside each one. A 70-degree day in March happens. So does snow on the tulips in mid-April. Pack for a range, not an average.

The numbers on this page are the official 1991-2020 climate normals for Chicago, which the National Weather Service measures at O'Hare. You'll find them on the NWS Chicago normals page and in NOAA's data files. For the week you're actually here, use the forecast from NWS Chicago. It's free and it doesn't have ads.

The lake changes everything

O'Hare sits out on the city's northwest edge, miles from the water, and that matters, because Lake Michigan runs the show along the shore. The Illinois State Water Survey's Chicago climate summary says the lake brings cooler summers and milder winters near the water. In spring and early summer the water is still cold, and when the wind comes off the lake, Streeterville, the Gold Coast and the beaches can sit well below the official high while the West Loop and the suburbs bake. Local TV forecasters say "cooler by the lake" so often it's basically a catchphrase. If a May forecast says 75, bring a layer for Navy Pier anyway.

In winter the lake works the other way. When winds blow from the north or northeast, they pick up moisture over open water and dump lake-effect snow on the city, heavier near the shore.

And the wind? Chicago's average wind speed at O'Hare is about 10 mph, which the same state climatologist's page says isn't much different from anywhere else around the Great Lakes. What you feel downtown is the tall buildings. The canyons along Wacker Drive and the bridges over the river funnel gusts that can knock a cheap umbrella inside out in January. Wind chill is the number to watch in winter, not the temperature.

Winter (December to early March)

Winter is why most tourists skip January through early March, and it's also why that's the cheapest time to come. Hotel rates drop, the museums are quiet, and you won't queue for anything except maybe brunch. Average highs sit in the low to mid 30s°F, with lows around 19 to 24°F, and O'Hare averages about 38 inches of snow a year, most of it from December through February. Those are averages. A cold snap with a few days below zero is normal enough that locals don't talk about it much. O'Hare averages six or seven nights a year that drop below 0°F.

The upside is the free stuff. The McCormick Tribune Ice Rink in Millennium Park is free to skate (you pay for rentals, and you need an online reservation), running from mid-November into early February. Christkindlmarket fills Daley Plaza from the Friday before Thanksgiving to Christmas Eve, and it has since added a second city market in Wrigleyville. Illinois residents get free days at most of the big museums, which we track on our free museum days page.

What to pack: a real winter coat that covers your hips, a hat that covers your ears, gloves, a scarf you can pull over your face, and waterproof boots with some grip. Salted sidewalks turn into slush, and sneakers get soaked in a block. See what to wear in Chicago in winter and Chicago in winter for more, plus winter activities and Christmas events.

Spring (March to May)

Spring kicks off with St. Patrick's Day, when the river gets dyed green, and the weather at that time of year is a coin toss. March averages a high of 47°F, but it can be 65 and sunny or 30 and sleeting. Snow is still possible into April, when highs average 59°F and rain picks up. May is the wettest month of the year at O'Hare, with about 4.5 inches, but it's also when highs reach 70°F and the city starts eating outside again. Remember the lake. A warm May day in the West Loop can feel like a different season on the lakefront path.

What to pack: layers. A light waterproof jacket, a sweater, and one warmer layer you can shed. An umbrella that can handle wind. More in what to wear in Chicago in spring and Chicago in spring.

Summer (June to August)

This is Chicago at its best, and everyone knows it, so it's also when hotels are priciest. Street festivals take over a different neighborhood nearly every weekend, restaurant patios fill up, and the Lakefront Trail is packed with runners and cyclists by 7am. Chicago Park District beaches have lifeguards from the Friday before Memorial Day through Labor Day, 11am to 7pm, according to the park district. Swimming is prohibited outside that season.

July is the hottest month, with an average high of 84.5°F and a low of 66°F. June and August aren't far behind. O'Hare averages about 17 days a year at 90°F or above, and humid heat waves push the heat index well past that. June and August are both wetter than July, and the rain usually comes as short, loud thunderstorms in the late afternoon that clear the air.

What to pack: breathable clothes, a swimsuit, sunscreen, and one long-sleeve layer for air-conditioned theaters and evenings by the water. See what to wear in Chicago in summer, Chicago in summer, beaches in Chicago and ways to beat the heat.

Fall (September to November)

If I had to pick one month to visit, it would be September. Highs average 75.5°F, the beaches are still there to walk even after lifeguards leave, and the summer crowds thin out once school starts. October cools to a 63°F average high with crisp nights, and the Chicago Marathon brings the city out to cheer (book your hotel early if you're coming that weekend). By November, highs are down to 48°F, the first snow is possible, and the Chicago Thanksgiving Parade runs down State Street on Thanksgiving morning. It was the McDonald's Thanksgiving Parade when this page was first written, but it no longer carries a sponsor's name.

What to pack: jeans, a sweater, and a medium jacket for September and October. Add a warmer coat, hat and gloves by November. More in what to wear in Chicago in fall and things to do in Chicago in fall.

Chicago weather by month

Average high, average low, precipitation and snowfall at O'Hare, 1991-2020 normals. Each month links to our guide for that month.

• January: high 31.6°F, low 18.8°F, 1.99 in. precipitation, 11.3 in. snow. The coldest month.
• February: high 35.7°F, low 21.8°F, 1.97 in. precipitation, 10.7 in. snow.
• March: high 47.0°F, low 31.0°F, 2.45 in. precipitation, 5.5 in. snow.
• April: high 59.0°F, low 40.3°F, 3.75 in. precipitation, 1.3 in. snow.
• May: high 70.5°F, low 50.6°F, 4.49 in. precipitation. The wettest month.
• June: high 80.4°F, low 60.8°F, 4.10 in. precipitation.
• July: high 84.5°F, low 66.4°F, 3.71 in. precipitation. The hottest month.
• August: high 82.5°F, low 65.1°F, 4.25 in. precipitation.
• September: high 75.5°F, low 57.1°F, 3.19 in. precipitation.
• October: high 62.7°F, low 45.4°F, 3.43 in. precipitation, a trace of snow on average.
• November: high 48.4°F, low 34.1°F, 2.42 in. precipitation, 1.8 in. snow.
• December: high 36.6°F, low 24.4°F, 2.11 in. precipitation, 7.6 in. snow.

For the year, that works out to an average high of 59.5°F, a low of 43.0°F, 37.86 inches of precipitation and 38.4 inches of snow. When it rains anyway, we've got a list of things to do in Chicago on rainy days.