The highest day temperature in September 2026 was 103°F. The lowest night temperature was 52°F. The average values for day and night temperatures during September were 78.7°F и 64.7°F respectivly.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Ottawa is 0.7 in. It makes september one of the least rainy months of the year.

The average wind speed in September is 8.2 mph. It makes September one of the most windless months of the year for Ottawa.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Ottawa in September is 8.4 hours.