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Canada weather

Weather in Ottawa for September 2025

Your guide to Ottawa weather in September - trends and predictions

    Temperatures

  • Until now, September 2025 in Ottawa is slightly cooler than the historical average by -0.8 °C.

  • The forecast for the next days in Ottawa predicts temperatures to be around 23 °C, close to the historical average.

  • In general, the average temperature in Ottawa at the beginning of September is 24.6 °C. As the month progressed, temperatures tended to significantly cool down, reaching an average of 21 °C by the end of September.

    • Rain 🌧️

  • Ottawa experiences moderate rainfall in September, with an average of 6 rainy days and a total precipitation of 75.7 mm.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
24
Dry days
Average rainy days
6
Rainy days
Average snowy days
0
Snow days
Average temperatures
22°/11°
Temperatures
Average wind speed
13 km/h
Avg max wind
Average humidity
74 %
Avg humidity

Ottawa Weather September

Move between months or click on a day
August
October
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Overcast
25°
2
Overcast
23°
3
Mist
25°
4
Overcast
27°
5
Mist
26°
6
Overcast
25°
7
Thundery outbreaks possible
21°
8
Light rain
18°
9
Cloudy
22°
10
Overcast
22°
11
Overcast
23°
12
Fog
23°
13
Mist
20°
14
Sunny
25°
15
Partly cloudy
23°
16
Partly cloudy
26°
17
Sunny
28°
18
Sunny
29°
19
Sunny
20°
20
Sunny
20°
21
Patchy rain possible
27°
22
Moderate rain
17°
23
Sunny
18°
24
Sunny
23°
25
Patchy rain possible
25°
26
Sunny
17°
27
Partly cloudy
19°
28
Partly cloudy
20°
29
Mist
21°
30
Partly cloudy
22°

Temperatures trend during September in Ottawa

See the weather trend as well as the moving average line

September weather in Ottawa day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
1 Sept. Overcast
Overcast
 25° /12° 1.9 mm 6
2 Sept. Overcast
Overcast
 23° /13° 0 mm 5
3 Sept. Mist
Mist
 25° /12° 0 mm 6
4 Sept. Overcast
Overcast
 27° /14° 1.8 mm 6
5 Sept. Mist
Mist
 26° /12° 0 mm 6
6 Sept. Overcast
Overcast
 25° /14° 0.1 mm 5
7 Sept. Thundery outbreaks possible
Thundery outbreaks possible
 21° /11° 5.4 mm 5
8 Sept. Light rain
Light rain
 18° /10° 1.4 mm 5
9 Sept. Cloudy
Cloudy
 22° /7° 0 mm 5
10 Sept. Overcast
Overcast
 22° /8° 0 mm 5
11 Sept. Overcast
Overcast
 23° /11° 0 mm 5
12 Sept. Fog
Fog
 23° /13° 0 mm 6
13 Sept. Mist
Mist
 20° /12° 0.1 mm 5
14 Sept. Sunny
Sunny
 25° /15° 0 mm 1.2
15 Sept. Partly cloudy
Partly cloudy
 23° /13° 0 mm 1.2
16 Sept. Partly cloudy
Partly cloudy
 26° /8° 0 mm 1.2
17 Sept. Sunny
Sunny
 28° /12° 0 mm 1.2
18 Sept. Sunny
Sunny
 29° /13° 0 mm 0
19 Sept. Sunny
Sunny
 20° /9° 0 mm 4
20 Sept. Sunny
Sunny
 20° /5° 0 mm 4
21 Sept. Patchy rain possible
Patchy rain possible
 27° /8° 4.5 mm 4
22 Sept. Moderate rain
Moderate rain
 17° /11° 6.6 mm 3
23 Sept. Sunny
Sunny
 18° /7° 0 mm 4
24 Sept. Sunny
Sunny
 23° /8° 0 mm 4
25 Sept. Patchy rain possible
Patchy rain possible
 25° /9° 0.4 mm 4
26 Sept. Sunny
Sunny
 17° /5° 0 mm 4
27 Sept. Partly cloudy
Partly cloudy
 19° /6° 0 mm 4
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
Next
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.
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Ottawa in September - FAQ

What are the expected maximum and minimum temperatures in Ottawa during September?
Enjoy moderate daytime temperatures of up to 22° 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?
Moderate rainfall is anticipated in Ottawa during September, with a total of 75.7 mm spread over approximately 6 days. Considering plans for rainy days is advisable.
What are the typical wind conditions in Ottawa during September?
The average wind speed in Ottawa during September is 13 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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