Will I be cold?
Will I be cold in San Antonio in January?
Verdict
Yes — Yes, cold.
Lows drop to 40°F on average — noticeably cold, especially after sundown.
Day vs. night
Day
62°F
Comfortable
A T-shirt and a light overshirt is enough.
Night
40°F
Cold
Cold enough that a hat and gloves become mandatory.
Why
San Antonio in January averages highs of 62°F, lows of 40°F, 8 rainy days.
Plan for real winter kit — an insulated coat, warm hat, and gloves rather than a light jacket.