When should I plant lettuce in ZIP 94102?

In ZIP 94102, the main lettuce target is around Jan 11, based on the representative San Francisco frost station and USDA zone 10a.

When should I start lettuce seeds indoors in 94102?

Start lettuce seeds indoors in ZIP 94102 around Dec 28, about 28 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 lettuce 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 lettuce around Jan 11; this uses the San Francisco frost station, USDA zone 10a, and lettuce 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 lettuce 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 lettuce seeds indoors in San Francisco

In ZIP 94102, start lettuce seeds indoors around Dec 28, about 28 days before the Jan 25 last-frost estimate.

Start lettuce seeds indoors in San Francisco around Dec 28, about 28 days before the Jan 25 last-frost estimate.

Seed starting schedule

Lettuce dates for San Francisco, CA

Step	Date	How to use it
Start Indoors	December 28, 2025	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	January 11, 2026	Move hardened-off seedlings outside after the frost-risk window.
Direct Sow	January 11, 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

Lettuce windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Dec 28

Direct sow

Jan 11

Transplant

Jan 11

Harvest

Mar 7

Frost watch

Oct 21

Reminder workflow

Every date has a next action

Start lettuce indoorsDec 28

Direct sow lettuceJan 11

Transplant lettuceJan 11

Last frost windowJan 25

First lettuce harvest windowMar 7

Last lettuce 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	8-12 in	Airflow and root space affect yield.
Soil temperature	40 F+	Seeds and transplants stall in cold soil.

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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

Lettuce timing notes

Succession sow every 10-14 days while weather is cool. Lettuce prefers sun to part shade, 8-12 in spacing, and soil near 40 F+.

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