| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 0.4° | -6.9° | 58.4mm | 11.8 | 8 |
| February | 2.7° | -5.3° | 57.7mm | 9.4 | 15 |
| March | 8.9° | 0° | 69.1mm | 11.2 | 39 |
| April | 15.4° | 5.2° | 102.6mm | 12.4 | 60 |
| May | 21.7° | 11.2° | 124.2mm | 12.6 | 75 |
| June | 27.3° | 17.1° | 110.9mm | 11 | 77 |
| July | 29.4° | 20° | 116.2mm | 9.9 | 71 |
| August | 28.4° | 19.4° | 102.7mm | 9.2 | 76 |
| September | 24.9° | 15.2° | 78.5mm | 7.9 | 84 |
| October | 17.7° | 8.3° | 97.2mm | 11 | 71 |
| November | 9.8° | 1.7° | 62.1mm | 9.6 | 48 |
| December | 3.3° | -3.8° | 61mm | 10.8 | 16 |
January in Oak Lawn averages a daily high of 0.4°C with nights around -6.9°C. Expect roughly 11.8 wet days totalling 58.4mm. A hard month to visit for comfort alone.
February in Oak Lawn averages a daily high of 2.7°C with nights around -5.3°C. Expect roughly 9.4 wet days totalling 57.7mm. A hard month to visit for comfort alone.
March in Oak Lawn averages a daily high of 8.9°C with nights around 0°C. Expect roughly 11.2 wet days totalling 69.1mm. Demanding conditions — pack for it and plan indoor options.
April in Oak Lawn averages a daily high of 15.4°C with nights around 5.2°C. Expect roughly 12.4 wet days totalling 102.6mm. Generally workable, with some weather to plan around.
May in Oak Lawn averages a daily high of 21.7°C with nights around 11.2°C. Expect roughly 12.6 wet days totalling 124.2mm. Comfortable conditions for being outdoors all day.
June in Oak Lawn averages a daily high of 27.3°C with nights around 17.1°C. Expect roughly 11 wet days totalling 110.9mm. Comfortable conditions for being outdoors all day.
July in Oak Lawn averages a daily high of 29.4°C with nights around 20°C. Expect roughly 9.9 wet days totalling 116.2mm. Generally workable, with some weather to plan around.
August in Oak Lawn averages a daily high of 28.4°C with nights around 19.4°C. Expect roughly 9.2 wet days totalling 102.7mm. Comfortable conditions for being outdoors all day.
September in Oak Lawn averages a daily high of 24.9°C with nights around 15.2°C. Expect roughly 7.9 wet days totalling 78.5mm. Comfortable conditions for being outdoors all day.
October in Oak Lawn averages a daily high of 17.7°C with nights around 8.3°C. Expect roughly 11 wet days totalling 97.2mm. Generally workable, with some weather to plan around.
November in Oak Lawn averages a daily high of 9.8°C with nights around 1.7°C. Expect roughly 9.6 wet days totalling 62.1mm. Demanding conditions — pack for it and plan indoor options.
December in Oak Lawn averages a daily high of 3.3°C with nights around -3.8°C. Expect roughly 10.8 wet days totalling 61mm. 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. Oak Lawn peaks at 84.
Based on 30 years of records, August–September scores highest for comfort in Oak Lawn, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29.4°C.
May is the wettest, averaging 124.2mm of rain across roughly 12.6 wet days.
January is the coolest month, with average daily highs around 0.4°C.