Hi Steph,
I am sorry to hear that you experienced colder weather in December/January as I was there in the beginning of December for our Panel training trip and I can tell you that although it was not too normal we did experience temperatures in the mid-80s and sunny almost every day! Typically, December normal highs are around 73F and January's normal highs are about 71F keeping in mind that these are the normal higher temperatures expected for these months but not always a guarantee and we experienced some near record highs during our trip!
You should have a bit more luck with going in September/October though to experience normal highs in temperatures ranging from 84F in October to 90F in September. September is just slightly cooler than August, and the chance of rain drops slightly as well. A September vacation in Orlando will include hot, humid weather, and some thunder storms. October sees big changes from prior months. The rainy season in Orlando is usually over by the beginning of October, and the temperatures are starting to drop. Rain is always a possibility in Orlando, but the probability is lower, the rain is less intense, and Orlando Weather In October is more pleasant than the months before.
That doesn't mean that the temperature will be cool, October is still quite warm. Temperatures warm enough for swimming are a nearly sure thing. Thunderstorms are still possible, even likely if you stay long enough.
September temperature trends are as follows: Record High 98F, Normal High 90F, Normal Low 81F and the Record Low is 57F. October temperature trends are as follows: Record High 95F, Normal High 84F, Normal Low 75F and the Record Low is 44F. If you hope to experience the Normal Highs and Lows you should definitely enjoy quite lovely weather during your vacation to Walt Disney World and I wish you a pixie dusted magical vacation!
Best wishes,
Brigitta