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Frost dates and planting calendar for Philadelphia, Pennsylvania

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
7b[1]
Median last spring frost
Mar 30[2]
Median first fall frost
Nov 17[3]
Growing season, median
232 days[4]

Philadelphia sits in USDA hardiness zone 7b[1]. The median last spring frost is March 30, based on NOAA records[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Mar 15, half of years Mar 30, 1 in 10 years after Apr 12Last frostmedian Mar 30First fall frost: 9 in 10 years before Dec 4, half of years Nov 17, 1 in 10 years before Nov 4First frostmedian Nov 17Frost riskHardyHardy vegetables: plant Mar 2 to Mar 16Mar 2 to Mar 16Semi-hardySemi-hardy vegetables: plant Mar 16 to Mar 30Mar 16 to Mar 30TenderTender vegetables: plant around Mar 30around Mar 30Very tenderVery tender vegetables: plant from Apr 13from Apr 13
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

Frost dates here come from NOAA climate normals for the Phila Franklin Inst weather station[5]. They are odds from 1991 to 2020, not promises. In half of years the last spring frost comes after March 30, and in 1 of 10 years it comes after April 12[2]. In fall, the first frost comes before November 17 in half of years and before November 4 in 1 of 10 years[3]. Any year can be earlier or later than these dates.

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after March 15 after March 30 after April 12
First fall frost (32°F)[3] before November 4 before November 17 before December 4
  • Hard freeze (28°F): median last spring date March 17, median first fall date November 29[7].
  • Frost-free growing season: at least 214 days in 9 of 10 years, 232 days in half of years and 255 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Phila Franklin Inst (USC00366886), 4.1 miles from the city center, 60 feet, 25 years of 1991 to 2020 records[5].

When to plant vegetables

The planting rules come from Colorado State University Extension, whose guide was written for Colorado[6]. GardenFacts applies them to the median last frost of March 30[6]. Hardy vegetables like peas, lettuce and spinach can go in as early as March 2 to March 16[6]. Semi-hardy vegetables like beets and carrots can go in as early as March 16, up to March 30[9]. Tomatoes, peppers and other very tender vegetables typically go in 2 or more weeks after the median last frost, with April 13 as the earliest start[10].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (March 30) is March 2 to March 16[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (March 30) is March 16, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, March 30[11]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (March 30), is April 13[10]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 2 May 6 (from transplants)
Cabbage (hardy)[12] Mar 2 May 26 (from transplants)
Kohlrabi (hardy)[12] Mar 2 Apr 21
Lettuce (hardy)[12] Mar 2 May 1
Onions (hardy)[12] Mar 2 Jun 20
Peas (hardy)[12] Mar 2 May 6
Radishes (hardy)[12] Mar 2 Apr 1
Spinach (hardy)[12] Mar 2 Apr 11
Turnips (hardy)[12] Mar 2 Apr 21
Beets (semi-hardy)[12] Mar 16 May 15
Carrots (semi-hardy)[12] Mar 16 May 25
Cauliflower (semi-hardy)[12] Mar 16 not listed
Parsnips (semi-hardy)[12] Mar 16 May 25
Potatoes (semi-hardy)[12] Mar 16 Jul 19
Swiss chard (semi-hardy)[12] Mar 16 May 15
Snap beans (tender)[12] Mar 30 May 29
Sweet corn (tender)[12] Mar 30 May 29
Cucumbers (tender)[12] Mar 30 May 24
Summer squash (tender)[12] Mar 30 May 19
Cantaloupe (very tender)[12] Apr 13 Jul 7
Eggplant (very tender)[12] Apr 13 Jun 12 (from transplants)
Peppers (very tender)[12] Apr 13 Jun 22 (from transplants)
Tomatoes (very tender)[12] Apr 13 Jun 17 (from transplants)
Winter squash (very tender)[12] Apr 13 Jul 22
Watermelon (very tender)[12] Apr 13 Jul 7
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

Philadelphia is in zone 7b on the USDA map, which means an average coldest winter night of 5°F to 10°F[1]. The zone is about winter cold, not summer heat or frost dates[14]. By land area, 100% of the city lies in ZIP code areas rated zone 7b[15].

Zone 7b: average annual extreme minimum temperature 5°F to 10°F (1991 to 2020)[1]. Modeled value at the city center: 8.6°F[1].

Share of the city's land area by ZIP code zone: zone 7b 100%[15].

All towns in zone 7b and what zone 7b means

Zone by ZIP code
ZIP code Zone Coldest night range
19153[15] 7b 5 to 10°F
19128[15] 7b 5 to 10°F
19154[15] 7b 5 to 10°F
19114[15] 7b 5 to 10°F
19131[15] 7b 5 to 10°F
19116[15] 7b 5 to 10°F
19115[15] 7b 5 to 10°F
19124[15] 7b 5 to 10°F
19111[15] 7b 5 to 10°F
19136[15] 7b 5 to 10°F
19145[15] 7b 5 to 10°F
19148[15] 7b 5 to 10°F
19144[15] 7b 5 to 10°F
19134[15] 7b 5 to 10°F
19119[15] 7b 5 to 10°F
19120[15] 7b 5 to 10°F
19140[15] 7b 5 to 10°F
19118[15] 7b 5 to 10°F
19143[15] 7b 5 to 10°F
19104[15] 7b 5 to 10°F
19152[15] 7b 5 to 10°F
19137[15] 7b 5 to 10°F
19151[15] 7b 5 to 10°F
19149[15] 7b 5 to 10°F
19121[15] 7b 5 to 10°F
19135[15] 7b 5 to 10°F
19132[15] 7b 5 to 10°F
19129[15] 7b 5 to 10°F
19112[15] 7b 5 to 10°F
19139[15] 7b 5 to 10°F

Questions people ask

What growing zone is Philadelphia?
The 2023 USDA map puts Philadelphia in zone 7b[1].
When is the last frost in Philadelphia?
The median last spring frost is March 30[2]. In 1 of 10 years the last frost comes after April 12[2].
When to plant tomatoes in Philadelphia?
CSU Extension says very tender vegetables like tomatoes typically go in 2 or more weeks after the average last frost[10]. For Philadelphia the earliest start is April 13[10].
When is the first frost in Philadelphia?
The median first fall frost is November 17[3]. In 1 of 10 years it comes before November 4[3].
How long is the growing season in Philadelphia?
In half of years the growing season is at least 232 days[4]. In 9 of 10 years it is at least 214 days[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Philadelphia, Pennsylvania in zone 7b. Zone 7b means an average annual extreme minimum temperature of 5°F to 10°F over 1991 to 2020. The map's modeled value at the city center is 8.6°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after March 15, in half of years after March 30, and in 1 of 10 years after April 12 (NOAA 1991 to 2020 normals). The median last frost date is March 30. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before November 4, in half of years before November 17, and in 9 of 10 years before December 4 (NOAA 1991 to 2020 normals). The median first frost date is November 17. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 214 days in 9 of 10 years, at least 232 days in half of years, and at least 255 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Phila Franklin Inst weather station (USC00366886), 4.1 miles from the center of Philadelphia at 60 feet, using 25 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is March 17 and the median first fall date is November 29. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Philadelphia, Pennsylvania overlaps 40 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 7b. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.