Weather and climate in Roselle, IL
What the weather is like in Roselle
The warmest month in Roselle is July, with average highs of 84°F. The coolest is January, when nights average 14°F. About 38.6 in of rain and snow falls in a typical year, most in May and least in January.
Skies are clearest in September (47% average cloud cover) and cloudiest in December (71%). Combining cloud with the length of truly dark nights, September, October, November offer the most clear, dark hours for stargazing.
Clear, dark hours per night
Hours of full astronomical darkness in mid-month, multiplied by the average share of clear sky. A rough guide to how much good observing time a typical night offers.
Monthly averages
| Month | High | Low | Precipitation | Cloud cover | Humidity | Wind | Dark hours |
|---|---|---|---|---|---|---|---|
| January | 30°F | 14°F | 1.7 in | 67% | 87% | 9 mph | 11.2 h |
| February | 33°F | 16°F | 2.0 in | 65% | 85% | 9 mph | 10.2 h |
| March | 45°F | 27°F | 2.5 in | 64% | 80% | 9 mph | 8.9 h |
| April | 58°F | 37°F | 3.7 in | 62% | 76% | 9 mph | 7.2 h |
| May | 69°F | 48°F | 4.7 in | 63% | 76% | 7 mph | 5.5 h |
| June | 79°F | 59°F | 4.4 in | 56% | 74% | 6 mph | 4.4 h |
| July | 84°F | 64°F | 3.9 in | 48% | 72% | 5 mph | 4.9 h |
| August | 83°F | 63°F | 4.2 in | 48% | 72% | 5 mph | 6.6 h |
| September | 75°F | 55°F | 3.4 in | 47% | 74% | 6 mph | 8.4 h |
| October | 61°F | 42°F | 3.6 in | 60% | 76% | 7 mph | 9.8 h |
| November | 47°F | 31°F | 2.3 in | 64% | 81% | 8 mph | 11.0 h |
| December | 34°F | 21°F | 2.2 in | 71% | 87% | 8 mph | 11.5 h |
Climate averages: NASA POWER, 2001–2025, for the grid area around 42.00, -88.13 (about 50 km across). High and low temperatures are estimated from the monthly mean and the average daily range. Hills, coasts and cities can differ from the area average. Aurora outlook for Roselle · Sources and methods.