Ottawa weather in September 2025

Expect 20°C daytime maximum temperatures in the shade with on average 6 hours of sunshine per day in Ottawa in September. Check more long-term weather averages for Ottawa in September before you book your next holiday to Ontario in 2025/2026.

  • 20°C maximum daytime temperature in September in Ottawa20
    20°C max day temperature
  • 6 hours of sunshine per day
  • 12 days with some rainfall in September in Ottawa12
    12 days with some rainfall
  • 9°C minimum night-time temperature in September in Ottawa9
    9°C min night temperature
  • 12 hours of daylight per day in September in Ottawa12
    12 hours of daylight per day
  • No heat & humidity in September in Ottawa0
    No heat & humidity
  • 80 mm monthly rainfall in September in Ottawa80
    80 mm of monthly rainfall
  • UV (maximum) index 5 (Moderate) in September in Ottawa5
    5 (Moderate) UV index

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The September weather guide for Ontario (Ottawa) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm)  |  Imperial (°F / inches)

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How hot is it in Ottawa in September?

Daytime temperatures usually reach 20°C in Ottawa in September, falling to 9°C at night.

How sunny is it in Ottawa in September?

There are normally 6 hours of bright sunshine each day in Ottawa in September - that's 46% of daylight hours.

Does it rain in Ottawa in September?

There are usually 12 days with some rain in Ottawa in September and the average monthly rainfall is 80mm.

Ottawa September sunrise & sunset times

Browse the sunrise and sunset times for Ottawa in September 2025. Select a month to view Ottawa sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:25 18:40
Monday, 15th September 2025 05:42 18:13
Tuesday, 30th September 2025 06:00 17:44

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