When should I plant tomatoes in ZIP 78205?

In ZIP 78205, the main tomatoes target is around Mar 8, based on the representative San Antonio frost station and USDA zone 9a.

When should I start tomatoes seeds indoors in 78205?

Start tomatoes seeds indoors in ZIP 78205 around Jan 18, about 42 days before the Mar 1 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 78205 planting calendar

When to plant tomatoes in San Antonio, TX - Zone 9a

Q: When is the first frost in San Antonio?

San Antonio (ZIP 78205) has an average first fall frost around Nov 20, leaving about 264 frost-free days.

In ZIP 78205, plant tomatoes around Mar 8; this uses the San Antonio frost station, USDA zone 9a, and tomatoes timing rules.

Your San Antonio calendar has a 264-day estimated frost-free season. This estimate uses the representative San Antonio frost station, USDA zone 9a, and tomatoes timing rules.

Source: san-antonio-intl frost station, USDA zone 9a, 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 9a San Antonio frost station Texas A&M AgriLife Extension Updated 2026-06-28

Read the method

Answer first

When to start tomatoes seeds indoors in San Antonio

In ZIP 78205, start tomatoes seeds indoors around Jan 18, about 42 days before the Mar 1 last-frost estimate.

Start tomatoes seeds indoors in San Antonio around Jan 18, about 42 days before the Mar 1 last-frost estimate.

Seed starting schedule

Tomatoes dates for San Antonio, TX

Step	Date	How to use it
Start Indoors	January 18, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	March 8, 2026	Move hardened-off seedlings outside after the frost-risk window.

Last frost

When is the last frost in San Antonio?

San Antonio (ZIP 78205) has an average last spring frost around Mar 1.

First frost

When is the first frost in San Antonio?

The average first fall frost is around Nov 20, giving about 264 frost-free days.

Season map

Tomatoes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Jan 18

Transplant

Mar 8

Harvest

May 25

Frost watch

Sep 3

Reminder workflow

Every date has a next action

Start tomatoes indoorsJan 18

Last frost windowMar 1

Transplant tomatoesMar 8

First tomatoes harvest windowMay 25

Last tomatoes sowing targetSep 3

Signal	Value	Why it matters
Last frost estimate	March 1, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	November 20, 2026	Fall planting counts backward from this date.
Season length	264 days	Longer seasons can support succession crops.
Spacing	18-24 in	Airflow and root space affect yield.
Soil temperature	60 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

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

Texas A&M AgriLife 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

Tomatoes timing notes

Harden seedlings off for a week before transplanting. Tomatoes prefers full sun, 18-24 in spacing, and soil near 60 F+.

For fall, count backward from Nov 20. A conservative last sowing target is around Sep 3.