Quick answer: For December racing in St. Petersburg, dress for a starting temperature in the mid-50s°F that climbs into the low-70s°F by mid-morning. Most runners do best in layers they can shed early, since the race starts cool but warms quickly under Florida sun.
St. Petersburg in December typically sees highs around 72°F and lows around 55°F, with crisp, low-humidity mornings, exactly the range that gives a marathon a real shot at ideal racing conditions. The catch is the swing: a comfortable 55°F start can feel noticeably warmer by the time you’re several miles in and the sun is up.
The core idea is simple: dress for how you’ll feel at mile 3, not how you feel standing at the start line. A throwaway layer solves the first cold mile without weighing you down for the rest of the race. If you’ve trained through a full block, this is the same instinct that should already be familiar from cool-morning training runs.
Even with a cool start, Florida sun is real by mid-morning. Sunscreen applied before the race, and a hat or visor if you’re sensitive to sun exposure, are worth the extra minute, especially for runners still out on the course two or more hours in.
Dress in layers, a light throwaway top for the cool start, shorts or lightweight tights, and gloves or a hat if you run cold. Plan to shed the extra layer once the race warms up.
Average lows sit around 55°F at the start, warming to around 72°F by mid-morning, a comfortable range for racing but enough of a swing to plan layers around.
Yes. Even with a cool start, Florida sun is strong by mid-morning. Sunscreen and a hat or visor are worth using, especially for runners on the course longer than two hours.