Ottawa weather in September 2026

Expect daytime maximum temperatures of 20°C in Ottawa, Ontario in September based on long-term weather averages. There are 6 hours of sunshine per day on average with 12 days with some rainfall and typically 80 mm of rainfall in the month.

  • 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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More about Ontario

How hot is it in Ottawa in September?

Daytime temperatures usually reach 21°C in Ottawa in September, falling to 11°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 48% of daylight hours.

How warm is the sea around Ottawa in September?

The average sea temperature around Ottawa in September is 19°C.

Does it rain in Ottawa in September?

There are usually 10 days with some rain in Ottawa in September and the average monthly rainfall is 75mm.

Ottawa September sunrise & sunset times

Browse the sunrise and sunset times for Ottawa in September 2026. Select a month to view Ottawa sunrise and sunset times for the next 12 months.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Tuesday, 1st September 2026 05:24 18:40
Tuesday, 15th September 2026 05:41 18:14
Wednesday, 30th September 2026 06:00 17:45

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