This includes the days when cloud covers up to 30% of the sky during daylight hours. For those with sensitive skin stay in the shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. (Hawaii vacation budget calculator), 9 Proven Strategies for Finding the Lowest Airfares to Hawaii. The months with the lowest UV index are January, February, March, April, May, June, July, August, October, November and December (UV index 6). ,