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Weather in Ottawa for September 2025

Your guide to Ottawa weather in September - trends and predictions
  • In general, the average temperature in Ottawa at the beginning of September is 25.3 °C. As the month progressed, temperatures tended to significantly cool down, reaching an average of 20.4 °C by the end of September.

  • With an average of 5 rainy days, Ottawa experiences minimal rainfall in September, ensuring that most days remain pleasantly dry.

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Average dry days
25
Dry days
Average rainy days
5
Rainy days
Average snowy days
0
Snow days
Average temperatures
23°/11°
Temperatures
Average wind speed
12 km/h
Avg max wind
Average humidity
72 %
Avg humidity

Ottawa in September average weather

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Temperatures trend during September in Ottawa

See the weather trend as well as the moving average line

September weather day by day

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Date Weather Temperatures Rain UV More
1 Sept. Overcast
Overcast
24° /10° 2.9 mm 6
2 Sept. Overcast
Overcast
22° /10° 0 mm 5
3 Sept. Mist
Mist
25° /10° 0 mm 7
4 Sept. Overcast
Overcast
27° /14° 0 mm 7
5 Sept. Mist
Mist
28° /15° 0 mm 7
6 Sept. Thundery outbreaks possible
Thundery outbreaks possible
28° /15° 0.2 mm 6
7 Sept. Thundery outbreaks possible
Thundery outbreaks possible
23° /12° 8.1 mm 5
8 Sept. Light rain
Light rain
16° /10° 2.2 mm 4
9 Sept. Cloudy
Cloudy
21° /7° 0 mm 5
10 Sept. Overcast
Overcast
21° /9° 0 mm 5
11 Sept. Overcast
Overcast
23° /9° 0 mm 5
12 Sept. Fog
Fog
24° /13° 0.1 mm 6
13 Sept. Mist
Mist
21° /12° 0.1 mm 6
14 Sept. Mist
Mist
21° /10° 0 mm 5
15 Sept. Partly cloudy
Partly cloudy
24° /10° 0 mm 6
16 Sept. Partly cloudy
Partly cloudy
25° /12° 0 mm 7
17 Sept. Patchy rain possible
Patchy rain possible
25° /13° 0.6 mm 6
18 Sept. Patchy light drizzle
Patchy light drizzle
23° /12° 0.8 mm 5
19 Sept. Thundery outbreaks possible
Thundery outbreaks possible
24° /14° 0 mm 6
20 Sept. Overcast
Overcast
21° /11° 0 mm 5
21 Sept. Mist
Mist
21° /9° 0 mm 5
22 Sept. Overcast
Overcast
22° /9° 0 mm 5
23 Sept. Mist
Mist
19° /11° 3.8 mm 5
24 Sept. Mist
Mist
22° /12° 0 mm 5
25 Sept. Sunny
Sunny
18° /10° 55 mm 5
26 Sept. Sunny
Sunny
20° /9° 2.1 mm 6
27 Sept. Mist
Mist
20° /9° 0 mm 5
28 Sept. Partly cloudy
Partly cloudy
20° /9° 0 mm 5
29 Sept. Mist
Mist
21° /9° 0 mm 5
30 Sept. Partly cloudy
Partly cloudy
22° /12° 0 mm 6
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Important Notice
Our weather forecast for Ottawa in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Ottawa forecast closer to your planned date for the most up-to-date weather information.

Ottawa in September - FAQ

What are the expected maximum and minimum temperatures in Ottawa during September?
Enjoy moderate daytime temperatures of up to 23° and cooler nights around 11°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Ottawa during September?
Expect minimal rainfall in Ottawa during September, with a total of 11.7 mm over approximately 5 days. This minimal precipitation is unlikely to significantly impact plans.
What are the typical wind conditions in Ottawa during September?
The average wind speed in Ottawa during September is 12 km/h, suggesting breezy to windy conditions, depending on your activities.

September rainfall patterns in Ottawa

Explore the daily rainfall trends and prepare for Ottawas September weather 💧

UV exposure in Ottawa during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Location coordinates Where is Ottawa?

Get accurate weather forecasts for Ottawa, located at latitude 45.411 and longitude -75.698. Stay updated with localized weather information tailored for Ottawa.

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