Chicago weather by month — averages, rainfall & climate trends
Strung along the shore of Lake Michigan in the American heartland, Chicago lives by a dramatic humid-continental climate — steamy summers, bitter snow-blown winters and a lake that softens both. Average temperatures and rainfall by month, a climate graph, today's conditions versus the long-term average, and how the climate has shifted since 1940 — all on one page for Chicago, United States.
Today vs average
−3.8°Cmuch cooler than usual
How it’s changed
Right now
What it's doing today vs the historical average for this date.
Right now
24.8°
25°20°
34°18°30°20°23°18°28°17°28°19°28°19°On this date — July 19
Cooler than usual · 3.8°C below the average high
- Record high: 35.3° · 1991
- Record low: 13.8° · 2024
- One year ago: 27.5°
Every July 19 in history — coldest to hottest
Dots show daily highs (top) and lows (bottom) for each July 19 on record (n = 87). Outlined dots are today's forecast.
Area we sample
Each city's history comes from one ERA5 grid cell — about 28 km across, shown by the dashed box. Near mountains or coasts, conditions can vary across the cell.
Location & data
Historical weather for Chicago is sampled from the ECMWF ERA5 reanalysis at 41.85°N, 87.65°W, with daily records since 1940.
- Coordinates
- 41.85°N, 87.65°W
- Time zone
- America/Chicago
- Period
- 1940–2026
- Data source
- ERA5 (ECMWF)
Last 30 days
16 of the last 31 days were warmer than the historical average for that date. Average difference: +0.2°C.
Each bar is one day, from morning low to afternoon high. Warm-colored bars are days whose mean ran above average; cool bars ran below. The dot inside the bar is the daily mean. The shaded band is the typical 10–90% range expected for that date. Average = the day's mean temperature averaged across every year of record (1940–2026) for that calendar date.
This date over the years
One dot per year — the mean temperature on this calendar date. Dots are warmer or cooler than the long-term average (dashed line); the shaded band is the typical 10–90% range, and the highlighted dot is today's forecast. Based on ERA5 reanalysis — modelled estimates, not station readings.
Weather by month
Average temperatures and rainfall for each month — what a typical year looks like, from the full record.Climate overview
Chicago sits on the southwestern shore of Lake Michigan on the flat plains of the American Midwest, where it has a hot-summer humid continental climate (Köppen Dfa). Summers are warm and humid, winters are cold and snowy, and the seasons swing widely as warm, moist air from the Gulf collides with cold continental outbreaks — a clash that fuels thunderstorms, blizzards and the occasional tornado. Lake Michigan moderates the immediate shoreline, cooling lakefront summer afternoons and easing the winter chill, and can spin up bands of lake-effect snow.
Extreme heat and cold both mark the record. The July 1995 heat wave was one of the deadliest in U.S. history, blamed for more than 700 deaths in the city, while the polar-vortex outbreak of January 2019 brought some of the most severe cold in decades. Heavy snowstorms, including the great blizzards of 1967 and 1979, periodically bury the city.
The warmest month is July, with a daily mean around 23.6°C and typical afternoon highs of 28.0°C. Roughly 20 days a year now top 30°C. In January, daily means drop to roughly -4.6°C, with nights dipping to -7.6°C.
In total, Chicago averages about 982 mm of precipitation a year; April is usually the wettest month (105 mm) and February the driest (53 mm).
Over the full record (since 1940), the annual mean temperature in Chicago has risen by 1.9°C between its first decade and its last. Frost days have thinned out, from around 120 a year in the first decade to about 90 now.
Climate graph (climograph)
July is the warmest month, January the coolest — a yearly swing of 28°C. Wettest month: April (~105 mm). Whole year averages ~982 mm of rain.
Bars = average monthly rainfall (right axis). Lines = average daily high and low (left axis). Average = each month's value averaged across every year of record (1940–2026).
Monthly wind
Average daily peak wind at 10 m, by month.
Monthly solar energy
Average daily incoming solar energy in megajoules per square metre — a measured proxy for how sunny the month is.
Chicago month by month — what to expect
Typical conditions for each month, averaged across the full record (since 1940). Daylight is the time from sunrise to sunset. Record high/low are the most extreme values in the ERA5 dataset (modelled since 1940), so they can differ from official weather-station readings.
| Month | Avg high | Avg low | Rain | Daylight | Record high | Record low |
|---|---|---|---|---|---|---|
| January | -0.8° | -7.6° | 61 mm | 9.3 h | 16.8° (2008) | -30.2° (1994) |
| February | 1.1° | -6.2° | 53 mm | 10.4 h | 20.5° (2024) | -27.1° (1951) |
| March | 6.6° | -1.2° | 81 mm | 11.7 h | 25.9° (2012) | -21.7° (2002) |
| April | 13.6° | 4.9° | 105 mm | 13.1 h | 28.8° (1986) | -9.5° (1982) |
| May | 20.1° | 11.3° | 103 mm | 14.4 h | 34.1° (2012) | -2.1° (1943) |
| June | 25.8° | 17.2° | 99 mm | 15.0 h | 37.6° (1988) | 5.6° (1945) |
| July | 28.0° | 19.9° | 91 mm | 14.8 h | 38.0° (1995) | 10.3° (1972) |
| August | 27.1° | 19.0° | 87 mm | 13.7 h | 36.5° (1988) | 7.8° (1965) |
| September | 23.4° | 14.8° | 78 mm | 12.3 h | 36.3° (1953) | 1.4° (1974) |
| October | 16.9° | 8.7° | 78 mm | 10.8 h | 30.6° (2007) | -4.6° (1962) |
| November | 8.9° | 2.1° | 75 mm | 9.6 h | 24.6° (1950) | -18.5° (1947) |
| December | 2.1° | -4.0° | 71 mm | 9.0 h | 19.0° (2012) | -29.0° (1983) |
How it has changed
Year-by-year signals from 1940 to today.Climate stripes
Annual mean shifted from 1940–1949 to 2016–2025 by +1.9°C.
Each vertical stripe is one year. Color encodes how much that year's annual mean differed from the long-term average. Average = each year's annual mean compared to the average of all years (1940–2026). cooler ← → warmer
Annual mean temperature
Long-term trend: +0.22°C per decade.
One point per year — the temperature averaged across the whole year. The dashed line is the least-squares long-term trend. Based on ERA5 reanalysis — modelled estimates, not station readings.
Seasonal warming
Dec–Feb is warming fastest: +0.34°C per decade.
Each faint line is one three-month period's average per year; the bold dashed line is its long-term trend. Different parts of the year often warm at different rates. Based on ERA5 reanalysis — modelled estimates, not station readings.
Hot days vs frost days
Days ≥ 30°C per year: 17.0 early in the record → 18.7 recently. Frost days: 119 → 88.
Thin lines are raw yearly counts; thick lines are the smoothed trend that removes year-to-year noise. The hot-day threshold is auto-picked per city so the line actually moves. Average = a centered 5-year rolling average to smooth weather noise.
Yearly hot & cold extremes
All-time high in 1995, all-time low in 1994: 38.0°C / -30.2°C.
One point per year — the single hottest and coldest day recorded that year.
Annual rainfall
~982 mm/year on average. Last decade ran +12% vs that average. Long-term trend: +23 mm per decade.
One bar per year of total rainfall. Dashed line is the long-term average. Average = the average annual rainfall across every year of record (1940–2026).
Day-by-day grid
Each tiny square is one calendar day across the full record — ~30,000 days per city. Use the mode switch above the chart: Anomaly colors each day by how far it ran from the historical average for that date (red = warmer, blue = cooler), Daily mean temp shows the absolute mean temperature for the day (useful to see seasons and heatwaves), and Precipitation shows daily rainfall (useful to spot wet/dry seasons and droughts). Average = the long-term average for that calendar date (1940–2026).