Orlando, Florida has amazing weather for most of the year. This is why Walt Disney decided to put Walt Disney World in Orlando in the first place.
For the majority of the year (the spring and fall ) it is warm and perfect weather for visiting the theme parks and water parks. There are some exceptions however, the winter can get quite cool (It has snowed while I was there before) and quite hot in the summer (I swear we were going to melt while watching a parade at the Magic Kingdom in July one year).
This is a graph of the average temperatures in the area Orlando from climate-zone.com
The average temperature is comfortable and it doesn't get to hot. You will most likely need a light jacket or sweater for the evenings.
You may get a little rain or a rainy day here and there - but not like in the summer.
Spring is my favorite time to visit as the weather is the best.
Orlando in the summer - June, July and August - is hot and humid. No way around it. Some people prefer it (not us) but we did visit at the end of July and beginning of August twice. I remember in Magic Kingdom one year we were watching the parade and it must have been 110 F.
You will also find more rain then in other seasons. The rain can sometime be categorized as "torrential downpour". You can watch the weather forecasts and plan those days as shopping days.
We broke up our days by going to the parks when they first opened, then at the hottest part of the day we would take a siesta and go back to our hotel. We would take a nap or go swimming. This was best with younger kids as they don't always do well with the heat (nor do we). We would then go back around dinner time (the parks were emptying out by then) and then stay until closing.
Disney and Universal also try to make it comfortable by providing cooling stations and misters in line ups.
So you can still make it work if you want to visit the parks etc. in the summer. It just takes some planning.
A note about Hurricanes - you never used to hear about hurricanes in the fall in Orlando - that only happened on the coasts. That seems to have changed recently. So again watch your weather watches.
Warren and I had a romantic weekend at Epcot in October right after 9/11. Now that may have contributed to it but the parks were empty and the weather was perfect!
In December, January, February, contrary to what you may think, the winter in Orlando and central Florida can be very cool. We spend most Christmases in Tampa with a couple of days in Orlando shopping at the outlet malls, and most years it is cool to cold. Jeans and jackets cool. And it can be windy making it feel cooler.
Don't get me wrong, we have had some nice warm days in the winter, but the majority have been cool. We like going to the parks etc, in the winter as we don't melt. But some days have been bitterly cold.
One New Year's Day one year, we were in a restaurant, with the wind ripping through the window next to us. It was like being at home it was so cold.
We enjoy the winters in Florida, even though it is cool. The way we look at it is that at least it is warmer than home and there is NO SNOW!