I live in SW FL. Every year, everyday the weather is different. Sometimes high in the 80's and sometimes low in the 30's. You cannot predict what it will be this coming December. You can say the averages will probably be 50-70 during the day and on the lower end at night. Can you swim, that's up to you. I own a heated pool and don't but the rest of my family always did. We've gone to Disney during the winter months and my family swam at night in the pools, I did not.