From January to May it is warm but usually rains more. Nevertheless, the number of rainy days in that period is still very limited. Moreover, the rain showers are usually short-lived.
From June through December it is drier but cooler.
The islands lie in a cold gulf stream that drifts westward from the southeastern Pacific Ocean at the height of the equator. Therefore, the water temperature sometimes drops between July and September.
Below is a climate table for the Galapagos Islands.