Hawaii · zones 12a–12a
When to plant watermelon in Hawaii.
Sow between Jan 22 to Mar 10 in a typical year, keyed to Hawaii's median last frost around Jan 1. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Watermelon dates for a typical Hawaii season.
Direct sow
Jan 22 to Mar 10
Keyed to the ~Jan 1 last frost. Sow 1" deep, 36" apart.
Harvest
~85 days later
~20 lb per plant over ~3 weeks.
Hawaii spans more than one climate: Zone 12 is the most common zone, but the state runs 12a to 12a. That's why the planner works from your ZIP code's frost dates, not your zone — mountain and coastal gardens in the same state can be three weeks apart.