Illinois Klimat and Average Väder
Klimat of Illinois: average temperatures, rainfall and seasons month by month.
Klimat in Illinois month by month
Average high, average low and total rainfall, based on three years of reanalysis data.
| Månad | Avg high | Avg low | Regnfall | Rating |
|---|---|---|---|---|
| januari | 1° | -7° | 62 mm | ★★☆☆☆ |
| februari | 8° | -3° | 20 mm | ★★★☆☆ |
| mars | 15° | 4° | 90 mm | ★★★☆☆ |
| april | 19° | 9° | 135 mm | ★★★☆☆ |
| maj | 24° | 13° | 100 mm | ★★★★☆ |
| juni | 28° | 19° | 117 mm | ★★★★☆ |
| juli | 29° | 21° | 129 mm | ★★★★☆ |
| augusti | 29° | 19° | 75 mm | ★★★★☆ |
| september | 28° | 17° | 33 mm | ★★★★★ |
| oktober | 20° | 10° | 37 mm | ★★★★☆ |
| november | 12° | 4° | 79 mm | ★★★☆☆ |
| december | 6° | -2° | 62 mm | ★★☆☆☆ |
Klimat type: Kontinental. Källa: Open-Meteo archive (ERA5).
Recent extremes in Illinois
Högest and lowest readings observed in the last 3 years of reanalysis data - not all-time records.
How Illinois compares med nearby places
Annual averages, and the difference against Illinois.
| Place | Distance | Avg temp | vs here | Annual rain |
|---|---|---|---|---|
| Gateway Arch National Park | 137 km | 15°C | +1°C warmer | 1156 mm |
| St. Louis | 137 km | 15°C | +1°C warmer | 1156 mm |
| Missouri | 255 km | 15°C | +1°C warmer | 1006 mm |
| Indianapolis | 298 km | 13°C | 1°C cooler | 1135 mm |
| Indiana | 298 km | 13°C | 1°C cooler | 1135 mm |
Klimat by city in Illinois
1 cities mapped in this atlas
Klimat by state park in Illinois
1 state and provincial parks mapped in this atlas
Klimat by county in Illinois
1 counties mapped in this atlas
Klimat by lake in Illinois
1 lakes mapped in this atlas
Bästa tiden att besöka Illinois
Go in augusti, september and oktober. These months score highest on comfortable temperatures, low rainfall and useful daylight.
Hardest months: januari, februari and december - expect the least comfortable mix of heat, cold or rain.
What this means for Illinois
Today is about average for september. The forecast high of 28°C is in line med the 28°C typical for this month.
A 18% 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 juni och augusti.
The gap between the warmest and coldest month averages 29°C.
What och pack, what och skip
- Lightweight, light-coloured clothing and a refillable water bottle
- sönglasses, a brimmed hat and SPF 30+
- Layers - the daily swing is 24°C, so mornings feel nothing like afternoons
- A packable rain shell - 2 of the next 7 days carry a real chance of rain
- If your dates are flexible, avoid januari, februari and december - historically the least comfortable months here.
Sammanfattning
Illinois is a state in USA. Illinois is a US state med huvudstad Springfield. Befolkningen är cirka 12.6 million. Huvudstaden är Springfield.
Just nu är det 23°C (73°F) in Illinois med mulet. Det känns som 24°C. I dag varierar temperaturen mellan 19°C och 28°C. Risken för nederbörd är 18%. Sightseeing conditions score 9.2/10 - utmärkt — åk nu.
Bästa tiden att besöka Illinois is augusti, september and oktober. Klimatet är continental. januari, februari and december tend och be the least comfortable months. juli is the warmest month med average highs near 29°C, while januari is the coldest med lows near -7°C.
The closest major airport is O'Hare International Airport (ORD), about 284 km away. Nearby highlights include Starved Rock State Park, Lake Michigan, Gateway Arch National Park and Indiana Dunes National Park.
Enkelt förklarat. Today is about average for september. The forecast high of 28°C is in line med the 28°C typical for this month. The best window och be outside is roughly 7 AM och 10 AM, when temperature, rain chance and wind line up best. fishing is the strongest bet in Illinois today at 9.4/10. 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 Illinois
| Typ | State |
|---|---|
| Land | USA |
| Kontinent | Nordamerika |
| Koordinater | 39°46′54.1″N 89°39′0.4″W (39.7817, -89.6501) |
| Capital | Springfield |
| Befolkning | 12.600.000 |
| Area | 149.995 km² |
| Abbreviation | IL |
| Tidszon | America/Chicago |
| Lokal tid | 8:56 PM (UTC-05:00) |
| Best months | augusti, september and oktober |
| Klimat | Kontinental |
Väder map for Illinois
Animated model layers. Pick a layer och load it.
Animated layers by Vindy. For pin-level detail and nearby places, see the interactive map below.
Explore Illinois
Every topic we hold for this place, and the same topic for the places around it.
Klimat for related places
Frequently asked questions
Where is Illinois?
Illinois is a state in USA. Its coordinates are 39.7817, -89.6501. It lies in Nordamerika.
What is the weather like in Illinois just nu?
It is currently 23°C (73°F) med mulet. Luftfuktighet is 65% and wind is 10 km/h.
When is the best time och visit Illinois?
augusti, september and oktober offer the most comfortable conditions in Illinois, which has a continental climate. januari, februari 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 8:56 PM.
How many people live in Illinois?
Illinois has a population of approximately 12.6 million.
What is the nearest airport och Illinois?
The closest airports are O'Hare International Airport (ORD), 284 km away and Nashville International Airport (BNA), 483 km away.
What are the top things och 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. |
|---|---|
| Prognos and observations | Open-Meteo (ECMWF and national models). |
| Luftkvalitet and pollen | Copernicus CAMS via Open-Meteo. US AQI scale. |
| Klimat averages | ERA5 reanalysis via the Open-Meteo archive, aggregated over 3 years. |
| Official alerts | US National Väder 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 30, 2026 at 8:56 PM local time. Live blocks refresh every 15 minutes; climate averages monthly.
