| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -0.6° | -8.3° | 34.9mm | 8.5 | 13 |
| February | 1.1° | -7.9° | 37.1mm | 8.2 | 14 |
| March | 7° | -2.4° | 60.2mm | 10.6 | 31 |
| April | 13.2° | 2.5° | 89.4mm | 12 | 54 |
| May | 19.2° | 8° | 106.8mm | 13 | 71 |
| June | 24.8° | 13.7° | 104.3mm | 11.4 | 77 |
| July | 27.2° | 16.8° | 97mm | 10.2 | 79 |
| August | 26.6° | 16.4° | 88.3mm | 11.7 | 77 |
| September | 23.1° | 12.5° | 90.7mm | 10.9 | 78 |
| October | 16.1° | 6.1° | 83.9mm | 11.7 | 64 |
| November | 9.2° | 0.2° | 49.6mm | 9.2 | 44 |
| December | 2.3° | -5.5° | 52.3mm | 9.2 | 15 |
January in Waukegan averages a daily high of -0.6°C with nights around -8.3°C. Expect roughly 8.5 wet days totalling 34.9mm. A hard month to visit for comfort alone.
February in Waukegan averages a daily high of 1.1°C with nights around -7.9°C. Expect roughly 8.2 wet days totalling 37.1mm. A hard month to visit for comfort alone.
March in Waukegan averages a daily high of 7°C with nights around -2.4°C. Expect roughly 10.6 wet days totalling 60.2mm. A hard month to visit for comfort alone.
April in Waukegan averages a daily high of 13.2°C with nights around 2.5°C. Expect roughly 12 wet days totalling 89.4mm. Demanding conditions — pack for it and plan indoor options.
May in Waukegan averages a daily high of 19.2°C with nights around 8°C. Expect roughly 13 wet days totalling 106.8mm. Generally workable, with some weather to plan around.
June in Waukegan averages a daily high of 24.8°C with nights around 13.7°C. Expect roughly 11.4 wet days totalling 104.3mm. Comfortable conditions for being outdoors all day.
July in Waukegan averages a daily high of 27.2°C with nights around 16.8°C. Expect roughly 10.2 wet days totalling 97mm. Comfortable conditions for being outdoors all day.
August in Waukegan averages a daily high of 26.6°C with nights around 16.4°C. Expect roughly 11.7 wet days totalling 88.3mm. Comfortable conditions for being outdoors all day.
September in Waukegan averages a daily high of 23.1°C with nights around 12.5°C. Expect roughly 10.9 wet days totalling 90.7mm. Comfortable conditions for being outdoors all day.
October in Waukegan averages a daily high of 16.1°C with nights around 6.1°C. Expect roughly 11.7 wet days totalling 83.9mm. Generally workable, with some weather to plan around.
November in Waukegan averages a daily high of 9.2°C with nights around 0.2°C. Expect roughly 9.2 wet days totalling 49.6mm. Demanding conditions — pack for it and plan indoor options.
December in Waukegan averages a daily high of 2.3°C with nights around -5.5°C. Expect roughly 9.2 wet days totalling 52.3mm. 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. Waukegan peaks at 79.
Based on 30 years of records, May–September scores highest for comfort in Waukegan, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 27.2°C.
May is the wettest, averaging 106.8mm of rain across roughly 13 wet days.
January is the coolest month, with average daily highs around -0.6°C.