When should I plant zucchini in ZIP 94102?

In ZIP 94102, the main zucchini target is around Feb 4, based on the representative San Francisco frost station and USDA zone 10a.

When should I start zucchini seeds indoors in 94102?

Start zucchini seeds indoors in ZIP 94102 around Jan 4, about 21 days before the Jan 25 last-frost estimate.

Is this a guaranteed planting date?

No. GrowZone uses frost-date estimates, hardiness zones, and crop timing rules for planning. Local microclimates and current weather can shift the right date.

ZIP 94102 planting calendar

When to plant zucchini in San Francisco, CA - Zone 10a

Q: When is the first frost in San Francisco?

San Francisco (ZIP 94102) has an average first fall frost around Dec 15, leaving about 324 frost-free days.

In ZIP 94102, plant zucchini around Feb 4; this uses the San Francisco frost station, USDA zone 10a, and zucchini timing rules.

Your San Francisco calendar has a 324-day estimated frost-free season. This estimate uses the representative San Francisco frost station, USDA zone 10a, and zucchini timing rules.

Source: san-francisco-downtown frost station, USDA zone 10a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

USDA zone 10a San Francisco frost station University of California Agriculture and Natural Resources Updated 2026-06-28

Read the method

Answer first

When to start zucchini seeds indoors in San Francisco

In ZIP 94102, start zucchini seeds indoors around Jan 4, about 21 days before the Jan 25 last-frost estimate.

Start zucchini seeds indoors in San Francisco around Jan 4, about 21 days before the Jan 25 last-frost estimate.

Seed starting schedule

Zucchini dates for San Francisco, CA

Step	Date	How to use it
Start Indoors	January 4, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	February 4, 2026	Move hardened-off seedlings outside after the frost-risk window.
Direct Sow	February 4, 2026	Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in San Francisco?

San Francisco (ZIP 94102) has an average last spring frost around Jan 25.

First frost

When is the first frost in San Francisco?

The average first fall frost is around Dec 15, giving about 324 frost-free days.

Season map

Zucchini windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Jan 4

Direct sow

Feb 4

Transplant

Feb 4

Harvest

Mar 31

Frost watch

Oct 21

Reminder workflow

Every date has a next action

Start zucchini indoorsJan 4

Last frost windowJan 25

Direct sow zucchiniFeb 4

Transplant zucchiniFeb 4

First zucchini harvest windowMar 31

Last zucchini sowing targetOct 21

Signal	Value	Why it matters
Last frost estimate	January 25, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	December 15, 2026	Fall planting counts backward from this date.
Season length	324 days	Longer seasons can support succession crops.
Spacing	24-36 in	Airflow and root space affect yield.
Soil temperature	65 F+	Seeds and transplants stall in cold soil.

GrowZone may earn from qualifying seed or supply links when real affiliate IDs are configured. No monetized links are active without disclosure.

Local data

Why this date changes by ZIP

San Francisco frost history and USDA zone 10a 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

Zucchini timing notes

One or two healthy plants can feed a household. Zucchini prefers full sun, 24-36 in spacing, and soil near 65 F+.

For fall, count backward from Dec 15. A conservative last sowing target is around Oct 21.