Will I be hot?
Will I be hot in San Diego in January?
Verdict
No — No, comfortable.
Highs cap at 66°F — no heat-management gear needed.
Day vs. night
Day
66°F
Comfortable
A T-shirt and a light overshirt is enough.
Night
49°F
Cool
You'll want a warm layer after sunset — not a heavy coat.
Why
San Diego in January averages highs of 66°F, lows of 49°F, 6 rainy days.
Temperature is comfortable across the day; pack for style and weather resistance, not heat management.