I've been there in January twice. Both times we arrived around the 22nd-23rd. The first time in 2010 it was hot every day, this year it was freezing. And I mean freezing, 0 degrees celsius in the mornings. It was sunny every day but big coat needed every day until around lunchtime. It warmed up a bit in the afternoons though.
It was funny when we arrived in Orlando and looked out the window of the plane and saw the guys unloading the plane were dressed like they were working in the South Pole. We just laughed and thought they were just lightweights not used to a bit of cool weather but the joke was on us when we walked out of the terminal and queued up for the taxi.