Climate averages 1991–2020
St. Catharines weather
in September.
A mild, moderately wet month: the 4th warmest and the 8th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in St. Catharines: daytime highs average 21.5°C and nights cool to about 15.5°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 85 mm of rain on roughly 10 days, which makes September a moderately wet month (the 8th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 33 min on an average September day.
The nearest other city in this atlas is Niagara Falls (16 km away). In September its highs average 21.2°C, about as warm as St. Catharines, with 85 mm of rain.
Among the 86 cities listed in Canada, St. Catharines ranks 6th of 86 for the warmest September highs and joint 42nd of 86 for the driest September (rainfall, lowest first). The mean September high of those 86 cities is 19.8°C; St. Catharines is 1.7°C warmer than that mean.
From September to October, average highs fall by 6.7°C to 14.8°C, and monthly rainfall rises from 85 mm to 92 mm.
The annual picture
September in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
St. Catharines climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | -0.3°C-6.0°C | -6.0°C | 75 | 11.9 | 9.49 h |
| February | 0.0°C-6.6°C | -6.6°C | 60 | 9.1 | 10.510 h |
| March | 4.2°C-2.8°C | -2.8°C | 73 | 10.4 | 11.912 h |
| April | 10.8°C3.0°C | 3.0°C | 97 | 11.7 | 13.413 h |
| May | 17.4°C9.5°C | 9.5°C | 83 | 11.4 | 14.615 h |
| June | 22.8°C15.9°C | 15.9°C | 91 | 11.1 | 15.315 h |
| July | 25.8°C19.4°C | 19.4°C | 88 | 10.8 | 15.015 h |
| August | 25.1°C19.1°C | 19.1°C | 75 | 9.9 | 14.014 h |
| September, selected | 21.5°C15.5°C | 15.5°C | 85 | 9.7 | 12.513 h |
| October | 14.8°C9.4°C | 9.4°C | 92 | 12.0 | 11.111 h |
| November | 8.2°C3.3°C | 3.3°C | 82 | 10.7 | 9.810 h |
| December | 2.9°C-1.7°C | -1.7°C | 77 | 11.6 | 9.19 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Niagara Falls in SeptemberCanada · 16 kmHigh 21.2°C · Low 14.8°C · 85 mm rain
- Amherst in SeptemberUnited States · 42 kmHigh 21.5°C · Low 14.2°C · 81 mm rain
- Stoney Creek in SeptemberCanada · 43 kmHigh 22.0°C · Low 14.1°C · 77 mm rain
- Buffalo in SeptemberUnited States · 43 kmHigh 21.1°C · Low 14.6°C · 85 mm rain
- Oakville in SeptemberCanada · 47 kmHigh 21.4°C · Low 14.7°C · 75 mm rain
- Cheektowaga in SeptemberUnited States · 50 kmHigh 21.4°C · Low 14.0°C · 81 mm rain
- Hamilton in SeptemberCanada · 50 kmHigh 21.6°C · Low 15.1°C · 77 mm rain
- Burlington in SeptemberCanada · 54 kmHigh 21.3°C · Low 14.2°C · 75 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for St. Catharines) is explained once on the St. Catharines year overview and on the Sources, method and limits page.