Quoted from BelizeNet:

"The overall climate of Belize can be described as sub-tropical. The humidity while high, is seldom oppressive for long and is most noticeable along the coast. The mean annual humidity is 83%, but many days the humidity is masked by the cooling sea breezes. The Belize coastal area is exposed to southeast tradewinds averaging 10-13 knots and attain an uncanny consistency during the month of July.

Temperatures in Belize range from 50°F to 95°F with an annual mean of 79°F. November to January are traditionally the coolest months with a 75°F average and May to September are the warmest at about a 81°F average. Location is a big factor for temperature as Cayo to the west can be several degrees colder then along the coast and during November at night, temperatures can fall to a beautiful 46°F in Cayo. In the mountains, the coldest days and nights might seem relatively very cold and blankets will definitely be needed at night. However, the mean annual temperatures on in the mountains is a perfectly comfortable 72°F."

For more detailed information, please visit BelizeNet.

For the current weather in Belize, please visit Yahoo! Weather.