Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Kailua-Kona to Iceland as you normally would.
In terms of precipitation, rainfall in Iceland ranges from 1.6 - 3.1 inches per month. January is typically the wettest month, when rainfall can reach 3.1 in. May is typically the driest time to visit Iceland when rainfall is around 1.6 in.
If weather is an important factor for your trip to Iceland, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 51.8 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 32.0 F).