Warm-Season Vegetable

When to Plant Watermelon in Hawaii

The ultimate summer treat. Watermelons need heat, space, and patience — but the payoff is pure joy.

The Short Answer

In Hawaii, watermelon planting dates vary by region. In Coastal Hawaii, your average last frost is around None, while Upcountry/Mountain sees its last frost around Rare. Since watermelon are frost-sensitive, start seeds indoors 3 weeks before your last frost, then transplant outside 2 weeks after frost danger has passed. Volcanic soils — extremely fertile but can be acidic. Excellent drainage on slopes. Varies dramatically by island and...

Hawaii Frost Dates

Your planting dates depend on which part of Hawaii you're in. Here are the frost date ranges by region:

Region	Zones	Last Frost (Spring)	First Frost (Fall)
Coastal Hawaii	11a, 11b, 12a, 12b, 13a	None	None
Upcountry/Mountain	10a, 10b, 11a	Rare	Rare

Watermelon Planting Schedule for Hawaii

Coastal Hawaii (Zones 11a, 11b, 12a, 12b, 13a)

Average last frost: None · Average first frost: None

Start Seeds Indoors

3 wks before frost

Transplant Outside

2 wks after frost

Direct Sow

3 wks after frost

Upcountry/Mountain (Zones 10a, 10b, 11a)

Average last frost: Rare · Average first frost: Rare

Start Seeds Indoors

3 wks before frost

Transplant Outside

2 wks after frost

Direct Sow

3 wks after frost

Growing Watermelon in Hawaii

Watermelon in Hawaii's Climate

Your climate is watermelon paradise. Florida is the nation's #1 producer. Plant transplants as early as January in south Florida, February in central. Sandy soils drain well for watermelons but need compost. The biggest challenge isn't heat — it's fusarium wilt in soils with previous melon crops. Rotate locations on a 5-year cycle.

Soil Considerations for Hawaii

Volcanic soils — extremely fertile but can be acidic. Excellent drainage on slopes. Varies dramatically by island and elevation. Make sure soil has warmed to at least 70°F before planting watermelon outside.

Hawaii Climate & Growing Season

Tropical. Year-round growing season at lower elevations. Elevation creates microclimates. Plant warm-season crops anytime. Watermelon cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.

Growing season length varies across Hawaii: Coastal Hawaii (11a, 11b, 12a, 12b, 13a) has a last frost around None, while Upcountry/Mountain (10a, 10b, 11a) sees frost end around Rare. This difference matters for watermelon — transplant timing shifts by several weeks across the state.

Growing Tips

Black plastic mulch warms soil faster. Check ripeness by looking for a yellow ground spot and listening for a hollow thump.

Companion Planting

Plant watermelon alongside these companions for better growth:

Corn Sunflowers Marigolds

Keep watermelon away from:

Potatoes

The Bottom Line

Watermelon can be grown successfully across Hawaii, but your exact planting dates depend on which region you're in. Coastal Hawaii gardeners should plan around a None last frost, while those in Upcountry/Mountain can typically plant later. For exact dates based on your zip code, use our free planting date finder.

Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026