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ZIP 95113 planting calendar

When to plant watermelon in San Jose, CA - Zone 9b

In ZIP 95113, plant watermelon around Mar 1; this uses the San Jose frost station, USDA zone 9b, and watermelon timing rules.

Your San Jose calendar has a 289-day estimated frost-free season. This estimate uses the representative San Jose frost station, USDA zone 9b, and watermelon timing rules.

Source: san-jose-mineta frost station, USDA zone 9b, 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 san-jose-mineta frost station and USDA zone 9b, last updated 2026-06-28.

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

USDA zone 9b San Jose frost station University of California Agriculture and Natural Resources Updated 2026-06-28
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Answer first

When to start watermelon seeds indoors in San Jose

In ZIP 95113, start watermelon seeds indoors around Jan 25, about 21 days before the Feb 15 last-frost estimate.

Start watermelon seeds indoors in San Jose around Jan 25, about 21 days before the Feb 15 last-frost estimate.

Seed starting schedule

Watermelon dates for San Jose, CA

StepDateHow to use it
Start IndoorsJanuary 25, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMarch 1, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowMarch 1, 2026Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in San Jose?

San Jose (ZIP 95113) has an average last spring frost around Feb 15.

First frost

When is the first frost in San Jose?

The average first fall frost is around Dec 1, giving about 289 frost-free days.

Season map

Watermelon windows by month

JanFebMarAprMayJunJulAugSepOctNovDec
Start indoors
Jan 25
Direct sow
Mar 1
Transplant
Mar 1
Harvest
May 30
Frost watch
Sep 2

Reminder workflow

Every date has a next action

Start watermelon indoorsJan 25
Last frost windowFeb 15
Direct sow watermelonMar 1
Transplant watermelonMar 1
First watermelon harvest windowMay 30
Last watermelon sowing targetSep 2
SignalValueWhy it matters
Last frost estimateFebruary 15, 2026Warm-season transplant risk starts falling after this window.
First frost estimateDecember 1, 2026Fall planting counts backward from this date.
Season length289 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

San Jose frost history and USDA zone 9b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

University of California Agriculture and Natural Resources 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 Dec 1. A conservative last sowing target is around Sep 2.