When should I plant tomatoes in ZIP 19103?

In ZIP 19103, the main tomatoes target is around Apr 17, based on the representative Philadelphia frost station and USDA zone 7b.

When should I start tomatoes seeds indoors in 19103?

Start tomatoes seeds indoors in ZIP 19103 around Feb 27, about 42 days before the Apr 10 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 19103 planting calendar

When to plant tomatoes in Philadelphia, PA - Zone 7b

Q: When is the first frost in Philadelphia?

Philadelphia (ZIP 19103) has an average first fall frost around Nov 5, leaving about 209 frost-free days.

In ZIP 19103, plant tomatoes around Apr 17; this uses the Philadelphia frost station, USDA zone 7b, and tomatoes timing rules.

Your Philadelphia calendar has a 209-day estimated frost-free season. This estimate uses the representative Philadelphia frost station, USDA zone 7b, and tomatoes timing rules.

Source: philadelphia-intl frost station, USDA zone 7b, 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 7b Philadelphia frost station Penn State Extension Updated 2026-06-28

Read the method

Answer first

When to start tomatoes seeds indoors in Philadelphia

In ZIP 19103, start tomatoes seeds indoors around Feb 27, about 42 days before the Apr 10 last-frost estimate.

Start tomatoes seeds indoors in Philadelphia around Feb 27, about 42 days before the Apr 10 last-frost estimate.

Seed starting schedule

Tomatoes dates for Philadelphia, PA

Step	Date	How to use it
Start Indoors	February 27, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	April 17, 2026	Move hardened-off seedlings outside after the frost-risk window.

Last frost

When is the last frost in Philadelphia?

Philadelphia (ZIP 19103) has an average last spring frost around Apr 10.

First frost

When is the first frost in Philadelphia?

The average first fall frost is around Nov 5, giving about 209 frost-free days.

Season map

Tomatoes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Feb 27

Transplant

Apr 17

Harvest

Jul 4

Frost watch

Aug 19

Reminder workflow

Every date has a next action

Start tomatoes indoorsFeb 27

Last frost windowApr 10

Transplant tomatoesApr 17

First tomatoes harvest windowJul 4

Last tomatoes sowing targetAug 19

Signal	Value	Why it matters
Last frost estimate	April 10, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	November 5, 2026	Fall planting counts backward from this date.
Season length	209 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

Philadelphia frost history and USDA zone 7b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Penn State 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 5. A conservative last sowing target is around Aug 19.