San Antonio · September
Run in the pre-dawn.
Average high is 90°F with a 73°F overnight low. Expect 15 rain days — plan around the radar. Humid heat punishes mid-morning — get out before sunrise for the only truly comfortable window.
Avg high / low
90° / 73°F
Humidity
67%
Rain days
15/mo
Wind
11 mph
What September feels like in San Antonio
Sunrise
07:19
Mid-month average
Sunset
19:38
Mid-month average
Time-of-day breakdown
Morning
Cool relative to the day's peak, but heat builds fast. By 10 AM you're already chasing comfort.
Midday
Heat peaks here. Skip unless you've got shade and pace tolerance.
Evening
Cools off after sunset but still warm. Good for easy efforts; avoid hard intervals if you're chasing pace.
What to wear running in San Antonio in September
The kit for September in San Antonio: light, breathable, and moisture-wicking — singlet or short-sleeve only, a water-resistant cap or jacket on standby.
September vs the surrounding months
vs August
-5° avg high
+3 rain days
San Antonio in August →
September
90°F avg high
15 rain days
Best: pre-dawn
vs October
+8° avg high
+3 rain days
San Antonio in October →
Frequently Asked Questions
What is the best time of day to run in San Antonio in September?+
Pre-dawn. Humid heat punishes mid-morning — get out before sunrise for the only truly comfortable window.
What's the average temperature in San Antonio in September?+
Average high 90°F, average low 73°F.
How does September compare to surrounding months in San Antonio?+
Compared to August (avg high 96°F), September is cooler. Compared to October (avg high 83°F), September is warmer.
Does it rain often in San Antonio in September?+
Expect about 15 measurable rain days in September, on average.