Chicago has a hot-summer humid continental climate with four dramatically distinct seasons shaped by its position on the southwestern shore of Lake Michigan. Summers are warm to hot and humid (July averages 29 C / 84 F). Winters are cold, windy, and snowy (January averages -6 C / 21 F) with lake-effect snow adding to system snow from passing storms. Spring and fall are transitional and unpredictable, with temperature swings of 20 C (36 F) in a single day not uncommon in April and October. The “Windy City” nickname actually originated from 19th-century political bluster rather than meteorology, but the lake breeze does produce genuinely windy conditions along the lakeshore. Here is the month-by-month breakdown.
Chicago Weather by Month: Temperature and Precipitation Data
| Month | Avg High | Avg Low | Rainfall | Snowfall | Sun Hours |
|---|---|---|---|---|---|
| January | -1 C (31 F) | -9 C (16 F) | 51mm | 28cm (11in) | 4 |
| February | 2 C (35 F) | -7 C (20 F) | 43mm | 23cm (9in) | 5 |
| March | 8 C (46 F) | -2 C (29 F) | 64mm | 15cm (6in) | 6 |
| April | 15 C (59 F) | 4 C (39 F) | 86mm | 3cm (1in) | 7 |
| May | 21 C (70 F) | 10 C (50 F) | 97mm | 0cm | 9 |
| June | 27 C (81 F) | 16 C (60 F) | 99mm | 0cm | 10 |
| July | 29 C (84 F) | 19 C (66 F) | 94mm | 0cm | 10 |
| August | 28 C (82 F) | 18 C (65 F) | 99mm | 0cm | 9 |
| September | 24 C (75 F) | 14 C (57 F) | 81mm | 0cm | 7 |
| October | 17 C (62 F) | 7 C (45 F) | 76mm | 1cm (trace) | 6 |
| November | 9 C (48 F) | 1 C (34 F) | 76mm | 5cm (2in) | 4 |
| December | 2 C (35 F) | -6 C (22 F) | 56mm | 23cm (9in) | 3 |
Winter: December through February
Chicago winters are genuinely cold. January averages -1 C (31 F) by day and -9 C (16 F) at night, but Arctic outbreaks can push temperatures below -18 C (0 F) for days at a stretch. Wind chills regularly drop to -25 C (-13 F) or lower along the lakefront. Snowfall averages 94cm (37 inches) annually, with January the snowiest month at 28cm (11 inches). Lake-effect snow can produce intense but localized bands that dump 15-30cm (6-12 inches) in a few hours on the Illinois side. Chicago’s infrastructure is built for this: the Pedway system connects 40+ blocks of downtown via heated underground walkways, and the CTA trains run through virtually all winter weather. For seasonal strategies, see the best time to visit Chicago guide.
Spring: March through May
Spring in Chicago is the most volatile season. March still sees snow (15cm / 6 inches average) with temperatures just reaching 8 C (46 F). April warms to 15 C (59 F) but can swing from near-freezing mornings to 25 C (77 F) afternoons in the same week. May is the first reliably pleasant month at 21 C (70 F) with blooming parks and the start of outdoor dining season. Spring rainfall is the heaviest of the year, peaking at 97-99mm in May and June. The “lake breeze” effect in spring can make the lakeshore 5-8 C (9-14 F) cooler than inland neighborhoods like Wicker Park or Logan Square, especially in April and May. See neighborhoods in Chicago for area-specific weather patterns.
Summer: June through August
Chicago summers are warm, humid, and the reason the city comes alive each year. July peaks at 29 C (84 F) by day and 19 C (66 F) at night, with humidity making it feel 2-3 C warmer. Heat waves can push temperatures to 35-38 C (95-100 F) with high humidity, typically lasting 3-5 days. The lake provides natural air conditioning: lakeshore neighborhoods average 3-5 C (5-9 F) cooler than inland areas during summer days. June and July are the rainiest months at 99mm and 94mm respectively, typically from afternoon thunderstorms that pass in an hour. August at 28 C (82 F) with decreasing humidity is the best summer month. This is the peak season for things to do in Chicago and the city’s major festivals.
Fall: September through November
September is arguably Chicago’s best month: 24 C (75 F) days, 14 C (57 F) nights, low humidity, and clear skies. The lake remains warm enough for sailing through late September. October cools to 17 C (62 F) with the first frost typically arriving by the third week. Fall foliage peaks in mid-to-late October in city parks and along the lakefront. November is the true transition to winter at 9 C (48 F), with gray skies and the first measurable snow (5cm / 2 inches). The Chicago events and festivals calendar peaks in September with multiple major events.
Chicago’s weather variability is extreme: the record high is 41 C (105 F) and the record low is -33 C (-27 F), a 74-degree Celsius swing. But the city’s infrastructure, from heated Pedways to air-conditioned museums, handles both extremes. The Chicago travel tips FAQ covers seasonal packing and extreme weather preparation.
