What’s the climate like in the Galapagos Islands?

There are two main seasons on the islands: wet and hot, and dry and cool.
December to May (inclusive) are hot and humid (28°C / 82.4°F average temperature); even though it is warm during the day there might be heavy rain showers that can last for 20 minutes or more. That is why the islands can be very lush and green at this time of the year. Consider using insect repellent while visiting the islands. The water temperature is perfect for swimming and/or snorkeling. It is a wise to use a T- shirt or dive top while in the water to prevent sunburn.

Between June and November, it is cooler and windy (24° C/ 75.2°F average although at noon it can reach 33°C / 91.4˚F). It is also the “garua” season (local term for occasional light drizzle) especially around the southern islands. You might want to consider bringing a light rainproof windbreaker.
The water temperature is also cooler (20°C / 68˚F) at this time of the year. This means it is the best time for snorkeling, since the cold waters are rich in nutrients for the marine ecosystem, but you might want to have a wetsuit to keep warm.