When should I plant radishes in ZIP 94102?

In ZIP 94102, the main radishes target is around Dec 28, based on the representative San Francisco frost station and USDA zone 10a.

When should I start radishes seeds indoors in 94102?

Radishes is usually direct-sown for ZIP 94102. Use the Dec 28 planting window instead of starting it indoors.

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 radishes 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 radishes around Dec 28; this uses the San Francisco frost station, USDA zone 10a, and radishes 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 radishes 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 radishes seeds indoors in San Francisco

In ZIP 94102, radishes is usually direct-sown around Dec 28 instead of started indoors.

Radishes is normally direct-sown in San Francisco. Use around Dec 28 as the outdoor planting window for ZIP 94102.

Seed starting schedule

Radishes dates for San Francisco, CA

Step	Date	How to use it
Direct Sow	December 28, 2025	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

Radishes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Direct sow

Dec 28

Harvest

Jan 25

Frost watch

Nov 17

Reminder workflow

Every date has a next action

Direct sow radishesDec 28

Last frost windowJan 25

First radishes harvest windowJan 25

Last radishes sowing targetNov 17

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	1-2 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

Radishes timing notes

Fast crop; harvest promptly before roots get woody. Radishes prefers full sun, 1-2 in spacing, and soil near 40 F+.

For fall, count backward from Dec 15. A conservative last sowing target is around Nov 17.