Would help if you told us where you would be staying...

Like others have said, it sucks... but sucks less on the SW side... which was unfortunately far from where I lived.

I lived there 3 years (in Kapaa). I think around Feb one year was when it rained relentlessly for 50 days in a row... but that is unusual. At any rate be ready for rain, wear bright clothing, and bring good front and rear lights for visibility.

Oh... MTB. Someone told me there is a new dirt trail that goes all the way from the W to N side fairly near the beach. Call the bike shop in Kapaa about that. Trails in the foothills are usually muddy and quite challenging.