Illinois Weather Forecast
Illinois weather: 73°F, clear. Hourly forecast, 14-day outlook, UV, air quality and the best time to visit.
Summary
Illinois is a state in United States. Illinois is a US state with its capital at Springfield. It has a population of about 12.6 million. The capital is Springfield.
Right now it is 73°F (23°C) in Illinois with clear. It feels like 69°F. Today runs from 58°F to 86°F. Chance of precipitation is 1%. Sightseeing conditions score 9.4/10 - excellent - go now.
The best time to visit Illinois is May, 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 85°F, while January is the coldest with lows near 19°F.
The closest major airport is O'Hare International Airport (ORD), about 177 mi away. Nearby highlights include Starved Rock State Park, Lake Michigan, Gateway Arch National Park and Indiana Dunes National Park.
In plain terms. Today is slightly warmer than average for September. The forecast high of 86°F is 6.3°F above the 80°F typical for this month. The best window to be outside is roughly 7 AM to 10 AM, when temperature, rain chance and wind line up best. stargazing is the strongest bet in Illinois today at 9.9/10. 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.
Active alerts for Illinois
Derived from the forecast. No official alert feed is wired for this country yet.
Weather in Illinois right now
Source: Open-Meteo. Updated 11:14 PM, Sep 14 local time.
See the Illinois forecast by time range
Next 24 hours
Hour-by-hour temperature, precipitation chance and wind.
16-day forecast for Illinois
Daily highs and lows, precipitation and UV.
| Day | Conditions | High / Low | Precip | Wind | UV |
|---|---|---|---|---|---|
| Mon, Sep 14 | ☁️ Overcast | 86° / 58° | 1% | 12 mph | 6 |
| Tue, Sep 15 | ☁️ Overcast | 98° / 71° | 22% | 12 mph | 6 |
| Wed, Sep 16 | 🌧️ Heavy drizzle | 86° / 74° | 30% · 0,1 in | 10 mph | 6 |
| Thu, Sep 17 | 🌦️ Drizzle | 95° / 71° | 16% · 0,0 in | 8 mph | 6 |
| Fri, Sep 18 | 🌦️ Light showers | 96° / 70° | 16% · 0,1 in | 11 mph | 6 |
| Sat, Sep 19 | ☁️ Overcast | 100° / 76° | 20% | 12 mph | 6 |
| Sun, Sep 20 | 🌧️ Heavy drizzle | 91° / 67° | 37% · 0,2 in | 20 mph | 5 |
| Mon, Sep 21 | 🌦️ Drizzle | 66° / 60° | 16% · 0,2 in | 11 mph | 1 |
| Tue, Sep 22 | 🌦️ Light drizzle | 65° / 58° | 7% · 0,0 in | 11 mph | 2 |
| Wed, Sep 23 | ☁️ Overcast | 71° / 51° | 14% | 14 mph | 6 |
| Thu, Sep 24 | ⛅ Partly cloudy | 75° / 50° | 10% | 12 mph | 6 |
| Fri, Sep 25 | ☁️ Overcast | 74° / 54° | 10% | 9 mph | 4 |
| Sat, Sep 26 | ⛅ Partly cloudy | 82° / 56° | 10% | 7 mph | 5 |
| Sun, Sep 27 | ☁️ Overcast | 84° / 59° | 13% | 7 mph | 5 |
| Mon, Sep 28 | 🌤️ Mainly clear | 88° / 64° | 10% | 12 mph | 5 |
| Tue, Sep 29 | ☁️ Overcast | 76° / 57° | 23% | 13 mph | 4 |
Climate in Illinois 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 | 33° | 19° | 2,4 in | ★★☆☆☆ |
| February | 46° | 27° | 0,8 in | ★★★☆☆ |
| March | 60° | 39° | 3,5 in | ★★★☆☆ |
| April | 67° | 48° | 5,3 in | ★★★☆☆ |
| May | 74° | 56° | 3,9 in | ★★★★☆ |
| June | 83° | 66° | 4,6 in | ★★★★☆ |
| July | 85° | 69° | 5,1 in | ★★★★☆ |
| August | 83° | 67° | 2,3 in | ★★★★☆ |
| September | 80° | 61° | 1,7 in | ★★★★☆ |
| October | 69° | 50° | 1,5 in | ★★★★☆ |
| November | 54° | 38° | 3,1 in | ★★★☆☆ |
| December | 43° | 29° | 2,4 in | ★★☆☆☆ |
Climate type: Continental. Source: Open-Meteo archive (ERA5).
Weather map for Illinois
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.
Air quality and pollen in Illinois
Air quality: Open-Meteo (CAMS). US AQI scale.
Sun, twilight and moon
Golden and blue hour are the standard photographic approximation around sunrise and sunset.
Best time to visit Illinois
Go in May, 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.
Weather by city in Illinois
1 cities mapped in this atlas
Weather by state park in Illinois
1 state and provincial parks mapped in this atlas
Weather by county in Illinois
1 counties mapped in this atlas
Weather by lake in Illinois
1 lakes mapped in this atlas
Explore Illinois
Every topic we hold for this place, and the same topic for the places around it.
Weather for related places
Frequently asked questions
Where is Illinois?
Illinois is a state in United States. Its coordinates are 39.7817, -89.6501. It lies in North America.
What is the weather like in Illinois right now?
It is currently 73°F (23°C) with clear. Humidity is 45% and wind is 10 mph.
When is the best time to visit Illinois?
May, August, September and October offer the most comfortable conditions in Illinois, which has a continental climate. January, February and December are usually the hardest months for outdoor plans.
What time zone is Illinois in?
Illinois observes America/Chicago (UTC-05:00). The local time is 11:14 PM.
How many people live in Illinois?
Illinois has a population of approximately 12.6 million.
What is the nearest airport to Illinois?
The closest airports are O'Hare International Airport (ORD), 177 mi away and Nashville International Airport (BNA), 300 mi away.
What are the top things to do in Illinois?
Popular options include Starved Rock State Park, Lake Michigan, Gateway Arch National Park and Indiana Dunes National Park.
What places are in Illinois?
Illinois covers 4 places in this atlas, including Chicago, Starved Rock State Park, Cook County and Lake Michigan.
Related articles
Data sources and methodology
| Place data | USPOTUS Atlas dataset (us-states) - 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 September 14, 2026 at 11:14 PM local time. Live blocks refresh every 15 minutes; climate averages monthly.
