There is no simple climate on the Island of Hawaii with the island experiencing 10 of the world's 15 climate zones. The positive side to this is that there really is no bad time of year to go to the Island of Hawaii, because visitors who find that they are encountering bad weather can simply move to another part of the island and enjoy their vacation.

The eastern or windward coast is the wettest while the west side of the island is much drier, parts even classified as desert. At sea level the day time highs vary between the mid 70s in the winter and the mid 80s in the summer. The temperature drops quickly at higher elevations. Places like the Volcano Nationals Park and town of "Volcano" are at 4000 ft and much cooler.

Visitors who wish to avoid the rainy season will want to travel to the Island of Hawaii during the late spring, summer and early fall months.  Rainy season begins in approximately November and continues through approximately March.  The side of the island with Hilo is the rainy side, seeing approximately ten inches of rain each month.  The Kona side of the island rarely sees rain outside of the rainy season.

Here are a few links to a variety of weather information for the islands of Hawaii.

National Weather Service Forecasts

Historic Rainfall and Temperatures