Thunder Bay weather in September
Temperature, rain and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: June – September
What is the weather like in Thunder Bay in September?
In September, Thunder Bay is mild: daytime highs average 18 °C, and nights cool down to about 13 °C. Expect around 6 hours of sunshine a day. Rain is frequent, with about 10 rainy days and 84 mm in total. All in all, September is a good month for a holiday in Thunder Bay.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 83 | 75 | 30 |
| Day | 22° | 18° | 10° |
| Night | 16° | 13° | 6° |
| Sun | 8 h | 6 h | 4 h |
| Rain days | 10 | 10 | 10 |
More details for September
- Daylight
- 12 h 40 min07:32 – 20:12
- UV index
- 4 · moderateclear sky, noon (estimate)All months
- Muggy days
- 1 daydew point 18 °C or moreAll months
- Wind
- 23 km/haverage daily peakAll months
- Cloud cover
- 58 %on averageAll months
- Hot days
- 0 days30 °C or more
- Snow days
- 0 days1 cm or more of fresh snowAll months
- Time zone
- UTC−4America/Toronto
How the score comes together
- Temperatureweight 50 %97 %
- Sunshineweight 20 %50 %
- Few rainy daysweight 30 %56 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- Sunscreen
- A jumper for the evenings
- Rain jacket or umbrella
Thunder Bay in September: quick answers
Is Thunder Bay hot in September?
No. In September, Thunder Bay is mild: daytime highs average 18 °C and nights drop to about 13 °C.
Does it rain much in Thunder Bay in September?
Rain is frequent, with about 10 rainy days and 84 mm in total.
Thunder Bay month by month
The whole year in Thunder BayAll destinations: CanadaWhere to go in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences