Boise · September
Run in the morning.
Comfortable average high of 80°F, dipping to 55°F at night. Comfortable conditions all day, but morning consistently delivers the best combination of cool air and clear skies.
Avg high / low
80° / 55°F
Humidity
39%
Rain days
4/mo
Wind
10 mph
What September feels like in Boise
Sunrise
07:25
Mid-month average
Sunset
19:54
Mid-month average
Time-of-day breakdown
Morning
Steady cool air, low wind, and good light. The standard runner window in most months.
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 Boise in September
The kit for September in Boise: shorts and a short-sleeve are the standard kit.
September vs the surrounding months
vs August
-11° avg high
+2 rain days
Boise in August →
September
80°F avg high
4 rain days
Best: morning
vs October
+15° avg high
-2 rain days
Boise in October →
Frequently Asked Questions
What is the best time of day to run in Boise in September?+
Morning. Comfortable conditions all day, but morning consistently delivers the best combination of cool air and clear skies.
What's the average temperature in Boise in September?+
Average high 80°F, average low 55°F.
How does September compare to surrounding months in Boise?+
Compared to August (avg high 91°F), September is cooler. Compared to October (avg high 65°F), September is warmer.
Does it rain often in Boise in September?+
Expect about 4 measurable rain days in September, on average.