Illinois Météo Prévisions
Illinois weather: 18°C, ciel dégagé. Par heure forecast, 14-day outlook, UV, air quality and the best time à visit.
Illinois weather in septembre
One of the best months à visit Illinois.
septembre runs 9°C warmer than the annual average in Illinois.
Météo map for Illinois
Animated model layers. Pick a layer à load it.
Animated layers by Venty. For pin-level detail and nearby places, see the interactive map below.
Climat in Illinois month by month
Average high, average low and total rainfall, based on three years of reanalysis data.
| Mois | Max moyenne | Min moyenne | Précipitations | Évaluation |
|---|---|---|---|---|
| janvier | 1° | -7° | 62 mm | ★★☆☆☆ |
| février | 8° | -3° | 20 mm | ★★★☆☆ |
| mars | 15° | 4° | 90 mm | ★★★☆☆ |
| avril | 19° | 9° | 135 mm | ★★★☆☆ |
| mai | 24° | 13° | 100 mm | ★★★★☆ |
| juin | 28° | 19° | 117 mm | ★★★★☆ |
| juillet | 29° | 21° | 129 mm | ★★★★☆ |
| août | 29° | 19° | 75 mm | ★★★★☆ |
| septembre | 28° | 17° | 33 mm | ★★★★★ |
| octobre | 20° | 10° | 37 mm | ★★★★☆ |
| novembre | 12° | 4° | 79 mm | ★★★☆☆ |
| décembre | 6° | -2° | 62 mm | ★★☆☆☆ |
Climat type: Continental. Source : Open-Meteo archive (ERA5).
Meilleur moment pour visiter Illinois
Go in août, septembre and octobre. These months score highest on comfortable temperatures, low rainfall and useful daylight.
Hardest months: janvier, février and décembre – expect the least comfortable mix of heat, cold or rain.
What à pack, what à skip
- dim.glasses, a brimmed hat and SPF 30+
- Layers – the daily swing is 19°C, so mornings feel nothing like afternoons
- If your dates are flexible, avoid janvier, février and décembre – historically the least comfortable months here.
How Illinois compares avec 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 |
Voir les prévisions de Illinois par période
Illinois weather – more answers
Explore Illinois
Every topic we hold for this place, and the same topic for the places around it.
Météo for related places
Frequently asked questions
Where is Illinois?
Illinois is a state in États-Unis. Its coordinates are 39.7817, -89.6501. It lies in Amérique du Nord.
What is the weather like in Illinois maintenant?
It is currently 18°C (64°F) avec ciel dégagé. Humidité is 39% and wind is 8 km/h.
When is the best time à visit Illinois?
août, septembre and octobre offer the most comfortable conditions in Illinois, which has a continental climate. janvier, février and décembre are usually the hardest months for outdoor plans.
What time zone is Illinois in?
Illinois observes America/Chicago (UTC-05:00). The heure locale is 2:59 PM.
How many people live in Illinois?
Illinois has a population of approximately 12.6 million.
What is the nearest airport à 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 à 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. |
|---|---|
| Prévisions and observations | Open-Meteo (ECMWF and national models). |
| Qualité de l’air and pollen | Copernicus CAMS via Open-Meteo. US AQI scale. |
| Climat averages | ERA5 reanalysis via the Open-Meteo archive, aggregated over 3 years. |
| Official alerts | US National Météo 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 octobre 24, 2026 at 2:59 PM heure locale. Live blocks refresh every 15 minutes; climate averages monthly.
