Will I be hot?
Will I be hot in Busan in January?
Verdict
No — No, comfortable.
Highs cap at 45°F — no heat-management gear needed.
Day vs. night
Day
45°F
Cold
Direct sun feels cool at best; shade is jacket weather.
Night
33°F
Cold
Cold enough that a hat and gloves become mandatory.
Why
Busan in January averages highs of 45°F, lows of 33°F, 6 rainy days.
Temperature is comfortable across the day; pack for style and weather resistance, not heat management.