We went for 3 weeks from 11th Jan this year, and it was quite chilly. I had to go out and buy warm knitwear (not a terrible chore). For 3 days in the middle of the holiday, temperatures went to 3' below freezing, and I had to go and buy garden fleece to cover our young mango & avocado trees, they warned on the news reports that these were particularly vunerable.
A few days later we went down to Boca Ratan and it was still warm & glorious there.

http://www.onlinefloridavillas.com/villas/1473.aspx