Ottawa · September
Run in the morning.
Comfortable average high of 71°F, dipping to 55°F at night. Humidity averages 76% — the limiting factor on most runs. Humidity rises with the sun — morning runs catch the driest, coolest window.
Avg high / low
71° / 55°F
Humidity
76%
Rain days
12/mo
Wind
9 mph
What September feels like in Ottawa
Sunrise
06:42
Mid-month average
Sunset
19:13
Mid-month average
Time-of-day breakdown
Morning
Coolest, driest air of the day. The window before sunrise is the most reliable comfortable hour.
Midday
Mild but UV and traffic peak. Workable if you don't mind shifting your pace.
Evening
Warm and runnable. Crowded routes but the air's typically calm.
What to wear running in Ottawa in September
The kit for September in Ottawa: shorts and a short-sleeve are the standard kit, a water-resistant cap or jacket on standby.
September vs the surrounding months
vs August
-6° avg high
-4 rain days
Ottawa in August →
September
71°F avg high
12 rain days
Best: morning
vs October
+13° avg high
-3 rain days
Ottawa in October →
Frequently Asked Questions
What is the best time of day to run in Ottawa in September?+
Morning. Humidity rises with the sun — morning runs catch the driest, coolest window.
What's the average temperature in Ottawa in September?+
Average high 71°F, average low 55°F.
How does September compare to surrounding months in Ottawa?+
Compared to August (avg high 77°F), September is cooler. Compared to October (avg high 57°F), September is warmer.
Does it rain often in Ottawa in September?+
Expect about 12 measurable rain days in September, on average.