Ecuador has four different regions, each with their own climate. They all have different temperatures, rainfall and seasons.
El Oriente weather (Amazon region) to the east of Ecuador has a humid and rainy climate. Average daytime temperatures are around 25 Celcius (81 F). The dry season varies by region, but is usually November to Febuary. Best time to visit is during the dry season. People enjoying adventuresports like kayaking should go during the wet season.
La Costa weather (Coastal Lowlands) to the west of Ecuador is usually warm, with temperatures averaging 25 Celcius (81 F). The humid rainy season is from December to May. Best time to visit the area is between June and August, eventhough this is the busiest season at the coast. In the Guayaquil area there are two seasons: a hot rainy period, lasting from January to May; and a cooler dry season, during the rest of the year.
La Sierra weather (Highlands) have a much cooler climate - and temperatures vary with altitude. The average summer temperature in Quito, Ecuador is about 16 Celcius (55 f), but can easily reach 25 Celcius (81 F). Rainfall in Quito consists of a maximum of two hours of rain, mainly in the late afternoon or evening.
The Galapagos Islands have a warm and relatively dry climate year round, with temperatures averaging 27 Celcius (85 F).