| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 0.6° | -5° | 36.2mm | 10.5 | 14 |
| February | 1.4° | -4.7° | 33.4mm | 8.8 | 17 |
| March | 5.1° | -1.3° | 40.7mm | 9.3 | 29 |
| April | 10.7° | 3.5° | 70.3mm | 10.9 | 48 |
| May | 16.8° | 8.7° | 60.9mm | 9.2 | 71 |
| June | 22.7° | 15° | 74.9mm | 9.6 | 81 |
| July | 26.1° | 18.7° | 64.8mm | 8.6 | 83 |
| August | 25.6° | 18.7° | 52.3mm | 7.8 | 84 |
| September | 22.1° | 15.3° | 63.3mm | 8 | 84 |
| October | 15.4° | 9.2° | 59.2mm | 10.5 | 64 |
| November | 8.9° | 3.3° | 49.9mm | 9.4 | 46 |
| December | 3.8° | -1.1° | 48mm | 11.2 | 21 |
January in St. Catharines averages a daily high of 0.6°C with nights around -5°C. Expect roughly 10.5 wet days totalling 36.2mm. A hard month to visit for comfort alone.
February in St. Catharines averages a daily high of 1.4°C with nights around -4.7°C. Expect roughly 8.8 wet days totalling 33.4mm. A hard month to visit for comfort alone.
March in St. Catharines averages a daily high of 5.1°C with nights around -1.3°C. Expect roughly 9.3 wet days totalling 40.7mm. A hard month to visit for comfort alone.
April in St. Catharines averages a daily high of 10.7°C with nights around 3.5°C. Expect roughly 10.9 wet days totalling 70.3mm. Demanding conditions — pack for it and plan indoor options.
May in St. Catharines averages a daily high of 16.8°C with nights around 8.7°C. Expect roughly 9.2 wet days totalling 60.9mm. Generally workable, with some weather to plan around.
June in St. Catharines averages a daily high of 22.7°C with nights around 15°C. Expect roughly 9.6 wet days totalling 74.9mm. Comfortable conditions for being outdoors all day.
July in St. Catharines averages a daily high of 26.1°C with nights around 18.7°C. Expect roughly 8.6 wet days totalling 64.8mm. Comfortable conditions for being outdoors all day.
August in St. Catharines averages a daily high of 25.6°C with nights around 18.7°C. Expect roughly 7.8 wet days totalling 52.3mm. Comfortable conditions for being outdoors all day.
September in St. Catharines averages a daily high of 22.1°C with nights around 15.3°C. Expect roughly 8 wet days totalling 63.3mm. Comfortable conditions for being outdoors all day.
October in St. Catharines averages a daily high of 15.4°C with nights around 9.2°C. Expect roughly 10.5 wet days totalling 59.2mm. Generally workable, with some weather to plan around.
November in St. Catharines averages a daily high of 8.9°C with nights around 3.3°C. Expect roughly 9.4 wet days totalling 49.9mm. Demanding conditions — pack for it and plan indoor options.
December in St. Catharines averages a daily high of 3.8°C with nights around -1.1°C. Expect roughly 11.2 wet days totalling 48mm. 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. St. Catharines peaks at 84.
Based on 30 years of records, June–September scores highest for comfort in St. Catharines, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 26.1°C.
June is the wettest, averaging 74.9mm of rain across roughly 9.6 wet days.
January is the coolest month, with average daily highs around 0.6°C.