There is literally no 'best time' to vist Maui. Weather is on an average 85 degrees Fahrenheit the entire year, however April - May and September - June is when the hangover of the tourist season begins. This is rather a wonderful and ideal time to visit Maui, especially for budget travellers. From December - March, tourists come in abundance, especially from the US mainland and Canada, i.e mostly from colder areas. April marks as the beginning of the 'traveller' time in Maui, when there is comparatively less crowd and hence, everything is a little cheaper.