Lanai is the most secluded of the Hawaiian Islands and falls directly in the shadow of its sister island Maui, greatly affecting its weather conditions. Lanai never really has continuous showers. The most rainfall occurs in the first three or four months of the year. Lanai is one of the driest of the Hawaiian Islands, which explains its sun-baked appearance.
You can count on a lot of sun during your visit to Lanai's beaches, no matter what the time of year. The beaches are typically very dry and are on average about ten degrees warmer than Lanai City. Due to the sheltering from the surrounding islands Lanai has relatively calm surf conditions. Water temperatures at Lanai's beaches range between the mid 70's F (24 C) in winter to 80 F (27 C) in summer.
The warmest month of the year in Lanai is September while the coldest month is February. Temperature variations between night and day are minimal. Rainfall is fairly evenly distributed throughout the year.