Having the same problem here it is the earliest we have ever gone. I usually go mid March, but I am going to pack for shorts everyday bring a sweatshirt and I will bring a pair of jeans and yoga type pants? I WILL bring bathing suits and plan on swimming.
We have been going last week of Feb, first week of March for 9 years. I'd say 90% of the time the weather has been very good. We have had a few days where we needed sweat shirts with jackets, with a high temp around 55, some days we needed rain gear, and other days spent at Blizzard Beach with temps in the 90's.
Being from New England, I would say it's kind of like October.
We dress warm for our flight, with jeans, shirt, sweatshirt, and jacket which we remove at the Orlando airport. That way, we don't have to pack as much.
We do swim every year. If the sun is out, it gets hot by around noontime.
We also pack sweat pant for evening walks, or cool mornings. If you can't stand chilly mornings and are going out for a length of time, wear your shorts under your sweats and carry a plastic shopping bag or something to carry them once it warms up. Keep an eye on the Weather Channel and bring your sweats or wear pants and/or a sweatshirt if you plan on staying out after the sun starts to go down, which is around 6:00 or so down there at that time of year. It gets cool very quickly without the sun.
My observations, hope it helps.