Will I be cold?
Will I be cold in Denver in September?
Verdict
Maybe — Chilly at times.
Lows near 48°F — cool mornings and evenings, comfortable afternoons. Big diurnal swing (29°F) — layers matter more than one warm coat.
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.
Layering wins here. A packable puffer plus a base layer handles the cool end without overheating in the middle of the day.
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 chilly evenings →
Denver in September outfit ideas from ForecastStyle.