August in Kailua-Kona is the warmest month of the year. In August, the weather in Kailua-Kona is typically warm. Average daily high temperature in August is about 25 degrees above zero. On average, Kailua-Kona has 25 partly cloudy, 4 sunny, 1 rainy, and 1 cloudy day in August. The rains are usually light.