Cook County Climate and Average Weather
Climate of Cook County: average temperatures, rainfall and seasons month by month.
Climate in Cook County month by month
Average high, average low and total rainfall, based on three years of reanalysis data.
| Month | Avg high | Avg low | Rainfall | Rating |
|---|---|---|---|---|
| January | 29° | 17° | 2,9 in | ★★☆☆☆ |
| February | 40° | 25° | 0,7 in | ★★★☆☆ |
| March | 51° | 34° | 4,1 in | ★★★☆☆ |
| April | 59° | 43° | 4,4 in | ★★★☆☆ |
| May | 67° | 51° | 2,7 in | ★★★★☆ |
| June | 79° | 64° | 5,0 in | ★★★★☆ |
| July | 82° | 68° | 5,0 in | ★★★★☆ |
| August | 79° | 66° | 3,1 in | ★★★★☆ |
| September | 75° | 61° | 3,6 in | ★★★★☆ |
| October | 64° | 50° | 3,1 in | ★★★★☆ |
| November | 50° | 38° | 2,7 in | ★★★☆☆ |
| December | 38° | 27° | 2,7 in | ★★☆☆☆ |
Climate type: Continental. Source: Open-Meteo archive (ERA5).
Recent extremes in Cook County
Highest and lowest readings observed in the last 3 years of reanalysis data - not all-time records.
How Cook County compares with nearby places
Annual averages, and the difference against Cook County.
| Place | Distance | Avg temp | vs here | Annual rain |
|---|---|---|---|---|
| Area Code 312 | 0 mi | 52°F | about the same | 40 in |
| Chicago | 0 mi | 52°F | about the same | 40 in |
| The Loop | 0 mi | 52°F | about the same | 40 in |
| ZIP Code 60601 | 1 mi | 52°F | about the same | 40 in |
| Wicker Park | 3 mi | 52°F | about the same | 38 in |
Best time to visit Cook County
Go in May, June, August, September and October. These months score highest on comfortable temperatures, low rainfall and useful daylight.
Hardest months: January, February and December - expect the least comfortable mix of heat, cold or rain.
What this means for Cook County
Today is about average for August. The forecast high of 81°F is in line with the 79°F typical for this month.
A 17% chance means most of the area stays dry; a passing shower is possible but short.
No weather-related travel disruption is expected today. Roads and airports should run normally.
Northern Hemisphere, so peak summer falls in June to August.
The gap between the warmest and coldest month averages 84°F.
What to pack, what to skip
- Lightweight, light-coloured clothing and a refillable water bottle
- Sunglasses, a brimmed hat and SPF 30+
- If your dates are flexible, avoid January, February and December - historically the least comfortable months here.
Summary
Cook County is a county in Illinois. Cook County is a county in the United States. It has a population of about 5.1 million.
Right now it is 67°F (19°C) in Cook County with clear. It feels like 68°F. Today runs from 64°F to 81°F. Chance of precipitation is 17%. Sightseeing conditions score 9.3/10 - excellent - go now.
The best time to visit Cook County is May, June, August, September and October. The climate is continental. January, February and December tend to be the least comfortable months. July is the warmest month with average highs near 82°F, while January is the coldest with lows near 17°F.
The closest major airport is O'Hare International Airport (ORD), about 16 mi away. Nearby highlights include Indiana Dunes National Park, Starved Rock State Park and Lake Michigan.
In plain terms. Today is about average for August. The forecast high of 81°F is in line with the 79°F typical for this month. The best window to be outside is roughly 9 AM to 12 PM, when temperature, rain chance and wind line up best. stargazing is the strongest bet in Cook County today at 9.5/10. No weather-related travel disruption is expected today. Roads and airports should run normally.
Compiled from this page's own data: atlas facts plus live Open-Meteo readings.
Quick facts about Cook County
| Type | County |
|---|---|
| State | Illinois |
| Country | United States |
| Continent | North America |
| Coordinates | 41°52′41.2″N 87°37′47.3″W (41.8781, -87.6298) |
| Population | 5.100.000 |
| Local time | 6:33 AM (UTC-05:00) |
| Best months | May, June, August, September and October |
| Climate | Continental |
Weather map for Cook County
Animated model layers. Pick a layer to load it.
Animated layers by Windy. For pin-level detail and nearby places, see the interactive map below.
Explore Cook County
Every topic we hold for this place, and the same topic for the places around it.
Climate for related places
Frequently asked questions
Where is Cook County?
Cook County is a county in Illinois. Its coordinates are 41.8781, -87.6298. It lies in North America.
What is the weather like in Cook County right now?
It is currently 67°F (19°C) with clear. Humidity is 82% and wind is 5 mph.
When is the best time to visit Cook County?
May, June, August, September and October offer the most comfortable conditions in Cook County, which has a continental climate. January, February and December are usually the hardest months for outdoor plans.
What time zone is Cook County in?
Cook County observes America/Chicago (UTC-05:00). The local time is 6:33 AM.
How many people live in Cook County?
Cook County has a population of approximately 5.1 million.
What is the nearest airport to Cook County?
The closest airports are O'Hare International Airport (ORD), 16 mi away.
What are the top things to do in Cook County?
Popular options include Indiana Dunes National Park, Starved Rock State Park and Lake Michigan.
Related articles
Data sources and methodology
| Place data | USPOTUS Atlas dataset (us-counties) - coordinates, hierarchy and facts. |
|---|---|
| Forecast and observations | Open-Meteo (ECMWF and national models). |
| Air quality and pollen | Copernicus CAMS via Open-Meteo. US AQI scale. |
| Climate averages | ERA5 reanalysis via the Open-Meteo archive, aggregated over 3 years. |
| Official alerts | US National Weather Service. |
| Method | Scores, comparisons and advice on this page are computed from the inputs above. Distances are straight-line. Nothing is estimated where data is missing - the block is simply not shown. |
Last updated August 23, 2026 at 6:33 AM local time. Live blocks refresh every 15 minutes; climate averages monthly.
