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ZIP 02108 planting calendar

When to plant watermelon in Boston, MA - Zone 7a

In ZIP 02108, plant watermelon around May 4; this uses the Boston frost station, USDA zone 7a, and watermelon timing rules.

Your Boston calendar has a 194-day estimated frost-free season. This estimate uses the representative Boston frost station, USDA zone 7a, and watermelon timing rules.

Source: boston-logan frost station, USDA zone 7a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

Reviewed by GrowZone Editorial. Calculated from the boston-logan frost station and USDA zone 7a, last updated 2026-06-28.

In the Boston area, watermelon timing follows the Boston frost window, so the local ZIP date can differ from a broad zone-only calendar.

USDA zone 7a Boston frost station UMass Extension Updated 2026-06-28
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Answer first

When to start watermelon seeds indoors in Boston

In ZIP 02108, start watermelon seeds indoors around Mar 30, about 21 days before the Apr 20 last-frost estimate.

Start watermelon seeds indoors in Boston around Mar 30, about 21 days before the Apr 20 last-frost estimate.

Seed starting schedule

Watermelon dates for Boston, MA

StepDateHow to use it
Start IndoorsMarch 30, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 4, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowMay 4, 2026Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Boston?

Boston (ZIP 02108) has an average last spring frost around Apr 20.

First frost

When is the first frost in Boston?

The average first fall frost is around Oct 31, giving about 194 frost-free days.

Season map

Watermelon windows by month

JanFebMarAprMayJunJulAugSepOctNovDec
Start indoors
Mar 30
Direct sow
May 4
Transplant
May 4
Harvest
Aug 2
Frost watch
Aug 2

Reminder workflow

Every date has a next action

Start watermelon indoorsMar 30
Last frost windowApr 20
Direct sow watermelonMay 4
Transplant watermelonMay 4
First watermelon harvest windowAug 2
Last watermelon sowing targetAug 2
SignalValueWhy it matters
Last frost estimateApril 20, 2026Warm-season transplant risk starts falling after this window.
First frost estimateOctober 31, 2026Fall planting counts backward from this date.
Season length194 daysLonger seasons can support succession crops.
Spacing36-60 inAirflow and root space affect yield.
Soil temperature70 F+Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Boston frost history and USDA zone 7a shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

UMass Extension is the kind of local source to verify against when a crop is expensive, weather is unusual, or your yard has a cold pocket.

Crop note

Watermelon timing notes

Wait for warm soil; watermelon stalls when nights stay cool. Watermelon prefers full sun, 36-60 in spacing, and soil near 70 F+.

For fall, count backward from Oct 31. A conservative last sowing target is around Aug 2.