http://www.hiloagent.com/rainmap.htm Big Island Hawaii Weather: There are a number of micro-climates here on Hawaii Island ranging from desert-like areas (complete with cactus) to occasional snow at the top of Mauna Kea and Mauna Loa. If you like tropical lush green and partly cloudy, or almost always warm sunny and dry, we have it all here on the Big Island of Hawaii!
Easy blowing trade winds often brings the windward Hilo side (East Hawaii) more rain and cooler temperatures than the leeward Kona side (West Hawaii) of the Island. It is cloudier and rainiest in the hills high above Hilo town, and warmer and dryer in the lower elevation areas near Hilo Bay and along the Puna coast. Volcano (upper Puna) weather is cooler due to the elevation and it is not unusual to see a stove or fireplace up there to use during the cooler winter nights. Areas along the Hamakua Coast, especially near Honokaa are quite temperate, although often cloudier and the evening rain begins earlier in the hills than along the coast. Don't be misled... an average Hilo day is a sunny morning, partly cloudy afternoon, and rain a few evenings and/or early mornings a week. The weather reports often forecast rain because at some point in the 24 hour day, there is likely to be some rainfall. A funny thing is when mainland clients ask "How can you live in an area that gets 75 to 125 inches of rain a year?" But after they spend a year here, they start praying for the rain to come back when we hit a dry spell! The rain keeps everything green, cool and fresh. It doesn't rain "all the time", but when it does, Hilo can get quite a downpour.
Kailua-Kona is typically a few degrees warmer and quite a bit more arid than tropical Hilo, and can stay warm well into the evening (unless you are higher up in the Kona hills.) It's almost always warm and sunny near the ocean, and partly cloudy in the hills. In parts of Kohala and Kona, a strong wind usually picks up in the late afternoons. To me, areas like Waikoloa in South Kohala are close to southern California like in weather. Waimea is pleasant during the day, and can sometimes be foggy, breezy and even chilly at night, especially on the "green side" of town. Homes in the higher elevation communities of Kona and Kohala may have fireplaces for those cooler winter nights. Kau and Kohala definitely have a green side and a brown side, and can be quite breezy at times at both the north and south points of the Island.
Our weather overall is quite pleasant year round - it just depends if you prefer to have more tropical, green and partly cloudy, or almost always full sun, warmer and very dry!