Weather will likely play an important role when you plan your trip to Kailua-Kona, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and September, with an average temperature of 24°C, while the coldest months are February and January, with an average of 22°C. The rainiest months in Kailua-Kona are August, June, July and May, with each month seeing an average of 268 mm of rainfall.