| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -0.5° | -9.1° | 48.7mm | 9.7 | 11 |
| February | 1.9° | -7.7° | 48.9mm | 8.1 | 14 |
| March | 8.8° | -2° | 60.7mm | 10.1 | 38 |
| April | 15.6° | 3.5° | 100.9mm | 12.3 | 61 |
| May | 21.7° | 9.5° | 125mm | 13.1 | 74 |
| June | 27.2° | 15.2° | 110.1mm | 11.4 | 76 |
| July | 29° | 17.6° | 115.6mm | 9.3 | 73 |
| August | 28.1° | 16.9° | 94.7mm | 9.1 | 77 |
| September | 24.9° | 12.7° | 78.6mm | 8.1 | 84 |
| October | 17.7° | 6° | 94mm | 9.8 | 73 |
| November | 9.3° | -0.4° | 60.7mm | 8.7 | 45 |
| December | 2.5° | -5.9° | 55.7mm | 9.9 | 13 |
January in Naperville averages a daily high of -0.5°C with nights around -9.1°C. Expect roughly 9.7 wet days totalling 48.7mm. A hard month to visit for comfort alone.
February in Naperville averages a daily high of 1.9°C with nights around -7.7°C. Expect roughly 8.1 wet days totalling 48.9mm. A hard month to visit for comfort alone.
March in Naperville averages a daily high of 8.8°C with nights around -2°C. Expect roughly 10.1 wet days totalling 60.7mm. Demanding conditions — pack for it and plan indoor options.
April in Naperville averages a daily high of 15.6°C with nights around 3.5°C. Expect roughly 12.3 wet days totalling 100.9mm. Generally workable, with some weather to plan around.
May in Naperville averages a daily high of 21.7°C with nights around 9.5°C. Expect roughly 13.1 wet days totalling 125mm. Generally workable, with some weather to plan around.
June in Naperville averages a daily high of 27.2°C with nights around 15.2°C. Expect roughly 11.4 wet days totalling 110.1mm. Comfortable conditions for being outdoors all day.
July in Naperville averages a daily high of 29°C with nights around 17.6°C. Expect roughly 9.3 wet days totalling 115.6mm. Generally workable, with some weather to plan around.
August in Naperville averages a daily high of 28.1°C with nights around 16.9°C. Expect roughly 9.1 wet days totalling 94.7mm. Comfortable conditions for being outdoors all day.
September in Naperville averages a daily high of 24.9°C with nights around 12.7°C. Expect roughly 8.1 wet days totalling 78.6mm. Comfortable conditions for being outdoors all day.
October in Naperville averages a daily high of 17.7°C with nights around 6°C. Expect roughly 9.8 wet days totalling 94mm. Generally workable, with some weather to plan around.
November in Naperville averages a daily high of 9.3°C with nights around -0.4°C. Expect roughly 8.7 wet days totalling 60.7mm. Demanding conditions — pack for it and plan indoor options.
December in Naperville averages a daily high of 2.5°C with nights around -5.9°C. Expect roughly 9.9 wet days totalling 55.7mm. A hard month to visit for comfort alone.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Naperville peaks at 84.
Based on 30 years of records, August–September scores highest for comfort in Naperville, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29°C.
May is the wettest, averaging 125mm of rain across roughly 13.1 wet days.
January is the coolest month, with average daily highs around -0.5°C.