Warm-Season Vegetable

When to Plant Watermelon in New Hampshire

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

The Short Answer

In New Hampshire, watermelon planting dates vary by region. In Northern New Hampshire, your average last frost is around May 20 - Jun 5, while Southern New Hampshire sees its last frost around May 1 - May 20. Since watermelon are frost-sensitive, start seeds indoors 3 weeks before your last frost, then transplant outside 2 weeks after frost danger has passed. Rocky, acidic New England soils. Glacial deposits. Granite bedrock. Raised beds essential in many areas.

New Hampshire Frost Dates

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

Region	Zones	Last Frost (Spring)	First Frost (Fall)
Northern New Hampshire	3b, 4a, 4b	May 20 - Jun 5	Sep 10 - Sep 25
Southern New Hampshire	5a, 5b, 6a	May 1 - May 20	Sep 25 - Oct 10

Watermelon Planting Schedule for New Hampshire

Northern New Hampshire (Zones 3b, 4a, 4b)

Average last frost: May 20 - Jun 5 · Average first frost: Sep 10 - Sep 25

Start Seeds Indoors

3 wks before frost

Transplant Outside

2 wks after frost

Direct Sow

3 wks after frost

Southern New Hampshire (Zones 5a, 5b, 6a)

Average last frost: May 1 - May 20 · Average first frost: Sep 25 - Oct 10

Start Seeds Indoors

3 wks before frost

Transplant Outside

2 wks after frost

Direct Sow

3 wks after frost

Growing Watermelon in New Hampshire

Watermelon in New Hampshire's Climate

Watermelon pushes the limits of cold-climate gardening. Choose short-season varieties only — Sugar Baby (75 days), Blacktail Mountain (75 days, bred for northern conditions). Start indoors 3 weeks before last frost. Black plastic mulch and row cover are essential. Expect smaller fruits than southern growers — but a sun-warmed watermelon from your own cold-climate garden is incomparably satisfying.

Soil Considerations for New Hampshire

Rocky, acidic New England soils. Glacial deposits. Granite bedrock. Raised beds essential in many areas. Make sure soil has warmed to at least 70°F before planting watermelon outside.

New Hampshire Climate & Growing Season

Short growing season especially in north. Cold winters. Cool summers. Hardy varieties important. 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 New Hampshire: Northern New Hampshire (3b, 4a, 4b) has a last frost around May 20 - Jun 5, while Southern New Hampshire (5a, 5b, 6a) sees frost end around May 1 - May 20. 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 New Hampshire, but your exact planting dates depend on which region you're in. Northern New Hampshire gardeners should plan around a May 20 - Jun 5 last frost, while those in Southern New Hampshire can typically plant earlier. 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