September weather forecastOttawa, Canada
September
Weather in September
September marks the official arrival of autumn in Ottawa. With the temperatures falling from those in August, the weather begins to cool down, heralding the upcoming fall. The early fall weather sees a decrease in the amount of daylight hours, witnessing the slow progression towards the year's colder months. Despite this, the city retains a bustling atmosphere as autumn paints its hues across Ottawa's landscape.Temperature
As Ottawa, Canada, enters September, the average high-temperature subtly lowers from the a warm 24°C (75.2°F) of August to a pleasant 20.2°C (68.4°F). In Ottawa, the average temperature during the nights of September drops to a fresh 10°C (50°F).Humidity
In Ottawa, the average relative humidity in September is 80%.Rainfall
September is the month with the least rainfall in Ottawa. Rain falls for 12.9 days and accumulates 54mm (2.13") of precipitation.Snowfall
June through September are months without snowfall.Daylight
In September, the average length of the day in Ottawa is 12h and 31min.On the first day of the month, sunrise is at 6:25 am and sunset at 7:39 pm. On the last day of September, sunrise is at 7:00 am and sunset at 6:44 pm EDT.
Sunshine
In Ottawa, Canada, the average sunshine in September is 8.8h.UV index
The average daily maximum UV index in September in Ottawa, Canada, is 3. A UV Index value of 3 to 5 symbolizes a moderate threat to health from unprotected exposure to Sun's UV rays for the average person.Note: In September, the maximum UV index of 3 suggests this advice:
Heed the precautions - Suggestions to avoid sunburn are made. The midday Sun can be harmful due to its potent UV radiation; seek shade and reduce exposure. On days when the sun blazes, arm yourself with sunglasses that block UVA and UVB radiation.
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Ottawa, Canada
- Average high temperature in September: 20.2°C
The warmest month (with the highest average high temperature) is July (25.3°C).
The month with the lowest average high temperature is January (-6.3°C).
- Average low temperature in September: 10°C
The month with the highest average low temperature is July (14.5°C).
The coldest month (with the lowest average low temperature) is January (-14.5°C).
Average pressure in September
Ottawa, Canada
- Average pressure in September: 1017.1mbar
The month with the highest atmospheric pressure is March (1018mbar).
The month with the lowest atmospheric pressure is June (1012.5mbar).
Average wind speed in September
Ottawa, Canada
- Average wind speed in September: 10.4km/h
The windiest month (with the highest average wind speed) is April (14km/h).
The calmest month (with the lowest average wind speed) is July (9.8km/h).
Average humidity in September
Ottawa, Canada
- Average humidity in September: 80%
The months with the highest relative humidity are January and February (91%).
The month with the lowest relative humidity is May (77%).
Average rainfall in September
Ottawa, Canada
- Average rainfall in September: 54mm
The wettest month (with the highest rainfall) is October (78mm).
The driest month (with the least rainfall) is September (54mm).
Average rainfall days in September
Ottawa, Canada
- Average rainfall days in September: 12.9 days
The month with the highest number of rainy days is July (17.1 days).
The month with the least rainy days is February (5.9 days).
Average snowfall in September
Ottawa, Canada
- Average snowfall in September: 0mm
The month with the highest snowfall is January (321mm).
The months with the least snowfall are June, July, August and September (0mm).
Average snowfall days in September
Ottawa, Canada
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is January (19.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in September /
Average sunshine in September
Ottawa, Canada
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 36min).
The month with the shortest days is December (Average daylight: 8h and 48min).
- Average sunshine in September: 8h and 48min
The month with the most sunshine is July (Average sunshine: 10h and 12min).
The month with the least sunshine is February (Average sunshine: 2h and 48min).
Average sunshine days in September
Ottawa, Canada
- Average sunshine days in September: 15 days
The month with the most sunshine days is September (15 days).
The month with the least sunshine days is February (9.1 days).
Average UV index in September
Ottawa, Canada
- Average UV index in September: 3
The months with the highest UV index are June, July and August (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 1).
Average cloud cover in September
Ottawa, Canada
- Average cloud cover in September: 37
The months with the most cloud cover are January and February (Cloud cover 69).
The month with the least cloud cover is July (Cloud cover 32).
Average visibility in September
Ottawa, Canada
- Average visibility in September: 8km
The months with the highest visibility are April, May, June, July, August and October (9km).
The months with the lowest visibility are January and February (7km).
