Will I be hot?
Will I be hot in Denver in September?
Verdict
Maybe — Warm at times.
Highs around 77°F — comfortable in shade, warm in direct sun. Big diurnal swing (29°F) — cool evenings save the day.
Day vs. night
Day
77°F
Warm
Breathable fabrics; sunscreen matters more than a jacket.
Night
48°F
Cool
You'll want a warm layer after sunset — not a heavy coat.
Why
Denver in September averages highs of 77°F, lows of 48°F, 7 rainy days.
Bring a light layer for the shade and a hat for the sun — the difference between them can feel like 15°F.
The day-to-night temperature swing is 29°F, which is the real story here — the average number hides how different midday and midnight feel.
See a full outfit plan for warm afternoons →
Denver in September outfit ideas from ForecastStyle.