GrowZone

Crop by USDA zone

When to plant watermelon in zone 12b

In USDA zone 12b, plant watermelon around Jan 15, after the representative last frost near Jan 1. Start seeds indoors around Dec 11.

This page summarizes the supported ZIPs in zone 12b. Your exact city can move earlier or later, so use the ZIP lookup for the frost-station-specific answer.

Get exact watermelon dates by ZIP code.

Seed starting schedule

Watermelon dates for Honolulu, HI

StepDateHow to use it
Start IndoorsDecember 11, 2025Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsJanuary 15, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowJanuary 15, 2026Sow seed outside when the crop and soil can handle the window.
Honolulu, HI · Zone 12b Watermelon Jan 15 Open ZIP-specific answer · last frost Jan 1