The main thing to remember is that once you leave the mainland and head out to sea the weather generally gets breezier and colder – so you’ll need the right clothing with you.
Always look at the forecast but remember than things can change more rapidly on an island.
Also the weather can be highly variable on one island. Leeward and seaward can be two different things.
Fog is the biggest challenge, particularly if you are on an island with a limited coastal path and you are relying on your navigation skills to circumnavigate.
Always check the forecast before you head out.