Illinois weather in January
January is one of the least pleasant months in Illinois: highs of 0°C (32°F) and about 48 mm (1.9 in) of rain on average. Nights average -5°C (23°F) and cloud cover 71% (NASA POWER, 2001–2025 averages). It is the driest month of the year and the coolest. Compared with December, it is cooler and drier; February brings highs of 0°C (33°F) and 54 mm (2.1 in) of rain.
Figures are long-term averages for Chicago, the largest city in Illinois. See below for other places.
Is January a good time to visit Illinois?
least pleasant month Weather score 38/100.
January is one of the least pleasant months for weather in Illinois. For better conditions, consider Jun–Sep.
Does it rain a lot in Illinois in January?
No, it is usually dry: about 48 mm (1.9 in) falls in an average January. It is the driest month of the year.
How warm is Illinois in January?
Days average 0°C (32°F) and nights -5°C (23°F).
Illinois weather by month
| Month | High | Low | Rain | Cloud | Weather |
|---|---|---|---|---|---|
| January | 0°C (32°F) | -5°C (23°F) | 48 mm | 71% | least pleasant |
| February | 0°C (33°F) | -5°C (23°F) | 54 mm | 70% | least pleasant |
| March | 5°C (41°F) | -1°C (31°F) | 62 mm | 66% | least pleasant |
| April | 10°C (50°F) | 4°C (39°F) | 95 mm | 63% | least pleasant |
| May | 15°C (59°F) | 9°C (47°F) | 117 mm | 64% | fair |
| June | 21°C (70°F) | 15°C (59°F) | 102 mm | 56% | best |
| July | 25°C (77°F) | 20°C (68°F) | 95 mm | 48% | best |
| August | 25°C (77°F) | 20°C (68°F) | 105 mm | 48% | best |
| September | 22°C (71°F) | 16°C (62°F) | 86 mm | 46% | best |
| October | 15°C (59°F) | 10°C (49°F) | 99 mm | 58% | fair |
| November | 9°C (47°F) | 4°C (38°F) | 61 mm | 63% | least pleasant |
| December | 3°C (37°F) | -2°C (29°F) | 58 mm | 73% | least pleasant |
Sources: 2001–2025 monthly averages from NASA POWER (MERRA-2 reanalysis). Page updated . How we rate months
Weather across Illinois in January
Weather can differ a lot within Illinois: coasts, hills and mountains each have their own climate.
| Place | High | Low | Rain | Weather |
|---|---|---|---|---|
| Chicago | 0°C (32°F) | -5°C (23°F) | 48 mm | least pleasant |
| Aurora | -1°C (29°F) | -10°C (14°F) | 44 mm | least pleasant |
| Rockford | -3°C (27°F) | -12°C (11°F) | 38 mm | least pleasant |
| Joliet | 0°C (31°F) | -9°C (15°F) | 48 mm | least pleasant |
| Naperville | -1°C (29°F) | -10°C (14°F) | 44 mm | least pleasant |
| Peoria | 1°C (33°F) | -8°C (17°F) | 52 mm | least pleasant |
| Springfield | 1°C (34°F) | -8°C (18°F) | 55 mm | least pleasant |
| North Peoria | 1°C (33°F) | -8°C (17°F) | 52 mm | least pleasant |
| Elgin | -1°C (29°F) | -10°C (14°F) | 44 mm | least pleasant |
| Waukegan | -2°C (28°F) | -10°C (13°F) | 42 mm | least pleasant |
| West Town | 0°C (32°F) | -5°C (23°F) | 48 mm | least pleasant |
| Champaign | 1°C (34°F) | -8°C (18°F) | 59 mm | least pleasant |