| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -2.2° | -9.2° | 72.2mm | 12.4 | 5 |
| February | -1° | -9.1° | 54.3mm | 8.7 | 13 |
| March | 4.1° | -4.6° | 59.1mm | 9.5 | 20 |
| April | 11.4° | 1° | 75.3mm | 10.5 | 50 |
| May | 18.9° | 7° | 72.8mm | 9.7 | 77 |
| June | 24.3° | 13.3° | 83mm | 10.9 | 78 |
| July | 26.4° | 14.9° | 90.7mm | 10.4 | 79 |
| August | 25.6° | 14.1° | 75.6mm | 10.1 | 80 |
| September | 21.7° | 10.3° | 81.5mm | 9.3 | 81 |
| October | 14° | 4.8° | 87.9mm | 12.9 | 55 |
| November | 6.6° | -0.9° | 77.4mm | 11.6 | 30 |
| December | 0.8° | -5.2° | 68.2mm | 11.8 | 11 |
January in Waterloo averages a daily high of -2.2°C with nights around -9.2°C. Expect roughly 12.4 wet days totalling 72.2mm. A hard month to visit for comfort alone.
February in Waterloo averages a daily high of -1°C with nights around -9.1°C. Expect roughly 8.7 wet days totalling 54.3mm. A hard month to visit for comfort alone.
March in Waterloo averages a daily high of 4.1°C with nights around -4.6°C. Expect roughly 9.5 wet days totalling 59.1mm. A hard month to visit for comfort alone.
April in Waterloo averages a daily high of 11.4°C with nights around 1°C. Expect roughly 10.5 wet days totalling 75.3mm. Demanding conditions — pack for it and plan indoor options.
May in Waterloo averages a daily high of 18.9°C with nights around 7°C. Expect roughly 9.7 wet days totalling 72.8mm. Comfortable conditions for being outdoors all day.
June in Waterloo averages a daily high of 24.3°C with nights around 13.3°C. Expect roughly 10.9 wet days totalling 83mm. Comfortable conditions for being outdoors all day.
July in Waterloo averages a daily high of 26.4°C with nights around 14.9°C. Expect roughly 10.4 wet days totalling 90.7mm. Comfortable conditions for being outdoors all day.
August in Waterloo averages a daily high of 25.6°C with nights around 14.1°C. Expect roughly 10.1 wet days totalling 75.6mm. Comfortable conditions for being outdoors all day.
September in Waterloo averages a daily high of 21.7°C with nights around 10.3°C. Expect roughly 9.3 wet days totalling 81.5mm. Comfortable conditions for being outdoors all day.
October in Waterloo averages a daily high of 14°C with nights around 4.8°C. Expect roughly 12.9 wet days totalling 87.9mm. Generally workable, with some weather to plan around.
November in Waterloo averages a daily high of 6.6°C with nights around -0.9°C. Expect roughly 11.6 wet days totalling 77.4mm. A hard month to visit for comfort alone.
December in Waterloo averages a daily high of 0.8°C with nights around -5.2°C. Expect roughly 11.8 wet days totalling 68.2mm. 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 81.
Based on 30 years of records, May–September scores highest for comfort in Waterloo, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 26.4°C.
July is the wettest, averaging 90.7mm of rain across roughly 10.4 wet days.
January is the coolest month, with average daily highs around -2.2°C.