April thru June and mid-August thru mid-September are Hawaii's "low seasons," and airfares are lower then. No matter what time of year you travel, you may be able to score better deals if you travel midweek.
How far in advance should I book for Hawaii?
In general, we recommend shopping for domestic flights 21 days to about 4 months out from your travel dates. However, Hawaii's popularity in the summer months (despite being an evergreen destination) coupled with the projected popularity this year makes shopping a little early a pretty solid plan.