Will I be cold?
Will I be cold in Denver in October?
Verdict
Yes — Yes, cold.
Lows drop to 37°F on average — noticeably cold, especially after sundown. Big diurnal swing (27°F) — layers matter more than one warm coat.
Day vs. night
Day
64°F
Comfortable
A T-shirt and a light overshirt is enough.
Night
37°F
Cold
Cold enough that a hat and gloves become mandatory.
Why
Denver in October averages highs of 64°F, lows of 37°F, 6 rainy days.
Plan for real winter kit — an insulated coat, warm hat, and gloves rather than a light jacket.
The day-to-night temperature swing is 27°F, which is the real story here — the average number hides how different midday and midnight feel.