Philadelphia frost dates and planting season

Name: Philadelphia
Address: Pennsylvania, United States

When to plant vegetables here. Cover calendars (fleece, cold frame, unheated greenhouse) are on each plant’s when-to-plant page.

Philadelphia has a long growing season, with roughly 214 frost-free days between the typical frost dates. Typical last spring frost: around April 17 (half of years later). Typical first fall frost: around November 18. Plant cool-season crops after about March 23; wait until about April 27 for warm-season crops.

Frost-free days214Apr 17 – Nov 18

Frost-free season in Philadelphia. Based on average frost dates. Adjust a week or two for your conditions.

Cover calendars (fleece, cold frame, unheated greenhouse) live on each crop’s when-to-plant page.

Weekly possible temperature4 – 99 °F

Frost-free days214

Typical last spring frostApril 17

Typical first fall frostNovember 18

Days suitable for warm-season vegetables182 (April 27 – October 25)

Days suitable for cool-season vegetables154 (March 23 – June 14; September 7 – November 15)

Calculated by Plan & Plant · Method · Data 2019–2026

Frost and suitability dates are typical figures from climate statistics. Microclimates vary; they are not a guarantee.

Frost dates calculated by Plan & Plant from Weather data by Open-Meteo.com (CC BY 4.0). Local frost pockets, valleys and coastal sites can differ by 1–3 weeks.

How we calculated this

Data: ERA5-Land via Open-Meteo, cell 39.95, -75.16, years 2019–2026 (not a 30-year climate normal yet).
Typical and safer dates: Typical last frost is the date after which half of winters in this sample had no more frost; safer is later in the sample so fewer winters still frosted.
Confidence: Provisional — short or thin sample for this place.
Full methodology (algorithm 2026-10-season-6).

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What to plant when

Cool-season vegetables

Earliest outdoor start: March 23

Suitable window: March 23 – June 14; September 7 – November 15

Cool-season crops prefer cooler weather.

Midsummer is often too hot, so suitable weeks split into more than one window.

See cool-season details

Warm-season vegetables

Earliest outdoor start: April 27

Suitable window: April 27 – October 25

Warm-season crops need mild or warm weather and cannot take frost.

Frost kills these crops, and cold snaps set them back.

See warm-season details

Green = usually good weeks to grow; blue or gray = usually too cold for that crop type.

Starter plants for Philadelphia

Cool-season

Radish Sow: March 6 – June 10; September 3 – September 30 Planting dates
Arugula Sow: March 6 – June 10; September 3 – September 17 Planting dates
Spinach Sow: March 6 – June 10 Planting dates
Lettuce Sow: March 6 – June 10 Planting dates
Kale Sow: March 6 – April 30 Planting dates
Beet Sow: March 20 – August 20 Planting dates

Warm-season

Zucchini Sow: May 22 – July 16 Planting dates
Cucumber Sow: May 22 – July 16 Planting dates
Green bean Sow: May 17 – August 11 Planting dates
Tomato Transplant: May 14 – July 8 Start indoors, then transplant. Planting dates
Bell pepper Transplant: May 22 – July 8 Start indoors, then transplant. Planting dates

How these dates are judged

Last frost: The typical last spring date when frost is still expected.
First frost: The typical first fall date when frost returns.
Frost-free days: The approximate days between those two dates.
Cool-season vegetables: Crops that prefer cooler weather, such as lettuce, kale, peas, and radish.
Warm-season vegetables: Crops that need warm weather and cannot take frost, such as tomato, pepper, squash, and beans.

Cool-season planting window

Mar 23 – Jun 14; Sep 7 – Nov 15 (154 days)

Warm-season planting window

Apr 27 – Oct 25 (182 days)

Usually too cold

January 1 – March 22
November 16 – December 31

Weekly temperatures and planting windows

Temperatures across the year for Philadelphia, with cool- and warm-season weeks and frost dates.

Possible min to max
Average min to max
Suitable
Tolerable
Too cold
Too hot

Selected week · tap a week or use the arrows

Week 13 · Mar 23 – Mar 29

Average 40 to 56 °F · Possible 24 to 79 °F

Cool season: tolerable

Warm season: too cold

A week is suitable for a crop type when its average low and high sit inside that type's range and its possible readings stay within the frost and heat limits (cool: 28 °F to 81 °F, warm: 32 °F to 90 °F); crossing a limit makes it tolerable, and for warm crops any chance of frost makes it too cold.

Based on average frost dates.

Pennsylvania, United States · 39.95, -75.16 · 2026

Coldest weekly possible temperature4 °F

Hottest weekly possible temperature99 °F

Last expected spring frostApril 17

First expected fall frostNovember 18

Show all 53 weeks