| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -2.5° | -12.2° | 30.4mm | 7.9 | 14 |
| February | 0° | -10.2° | 28.7mm | 7.7 | 15 |
| March | 7.7° | -3.4° | 49.7mm | 9.8 | 33 |
| April | 15.6° | 2.6° | 94.4mm | 11.1 | 64 |
| May | 22.1° | 9.4° | 119.2mm | 12.7 | 75 |
| June | 27.5° | 15.4° | 142.5mm | 11.8 | 74 |
| July | 29.1° | 17.2° | 100.5mm | 8.4 | 75 |
| August | 28° | 15.7° | 97.4mm | 8.5 | 79 |
| September | 24.9° | 11° | 74mm | 7.9 | 84 |
| October | 16.9° | 4° | 71mm | 8.4 | 73 |
| November | 8.3° | -2.9° | 42.8mm | 7.3 | 41 |
| December | 0.7° | -8.8° | 36.6mm | 8.3 | 13 |
January in Waterloo averages a daily high of -2.5°C with nights around -12.2°C. Expect roughly 7.9 wet days totalling 30.4mm. A hard month to visit for comfort alone.
February in Waterloo averages a daily high of 0°C with nights around -10.2°C. Expect roughly 7.7 wet days totalling 28.7mm. A hard month to visit for comfort alone.
March in Waterloo averages a daily high of 7.7°C with nights around -3.4°C. Expect roughly 9.8 wet days totalling 49.7mm. A hard month to visit for comfort alone.
April in Waterloo averages a daily high of 15.6°C with nights around 2.6°C. Expect roughly 11.1 wet days totalling 94.4mm. Generally workable, with some weather to plan around.
May in Waterloo averages a daily high of 22.1°C with nights around 9.4°C. Expect roughly 12.7 wet days totalling 119.2mm. Comfortable conditions for being outdoors all day.
June in Waterloo averages a daily high of 27.5°C with nights around 15.4°C. Expect roughly 11.8 wet days totalling 142.5mm. Generally workable, with some weather to plan around.
July in Waterloo averages a daily high of 29.1°C with nights around 17.2°C. Expect roughly 8.4 wet days totalling 100.5mm. Comfortable conditions for being outdoors all day.
August in Waterloo averages a daily high of 28°C with nights around 15.7°C. Expect roughly 8.5 wet days totalling 97.4mm. Comfortable conditions for being outdoors all day.
September in Waterloo averages a daily high of 24.9°C with nights around 11°C. Expect roughly 7.9 wet days totalling 74mm. Comfortable conditions for being outdoors all day.
October in Waterloo averages a daily high of 16.9°C with nights around 4°C. Expect roughly 8.4 wet days totalling 71mm. Generally workable, with some weather to plan around.
November in Waterloo averages a daily high of 8.3°C with nights around -2.9°C. Expect roughly 7.3 wet days totalling 42.8mm. Demanding conditions — pack for it and plan indoor options.
December in Waterloo averages a daily high of 0.7°C with nights around -8.8°C. Expect roughly 8.3 wet days totalling 36.6mm. 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. Waterloo peaks at 84.
Based on 30 years of records, August–September scores highest for comfort in Waterloo, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29.1°C.
June is the wettest, averaging 142.5mm of rain across roughly 11.8 wet days.
January is the coolest month, with average daily highs around -2.5°C.