Frost dates for Philadelphia, Pennsylvania
In Philadelphia, half of springs have had their last frost by April 4 (and 1 spring in 10 still has one after April 17), and half of falls have had their first frost by November 7, leaving about 216 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Philadelphia, Pennsylvania
Last spring frost
April 4
Half of springs have their last frost by this date. For a safer bet, wait until April 17: only 1 spring in 10 has a frost after that.
First fall frost
November 7
Half of falls have their first frost by this date. In 1 fall in 10 it comes by October 24.
Growing season
216 days
Frost-free days in a typical year. 9 years in 10 get at least 197.
Hardiness zone
7b
2023 USDA map: the coldest night of winter averages 5°F to 10°F. On the 2012 map it was 7a, half a zone colder. All 48 ZIP codes within about 6 miles of the city's center are in zone 7b.
Stations near you disagree. NOAA's Philadelphia Ne Airport (8 miles away, at 100 feet above sea level), the one we used, gives a typical last frost of April 4 and a typical first frost of November 7. NOAA's Neshaminy Falls (15 miles away, at 40 feet above sea level) gives a typical last frost of April 21 and a typical first frost of October 25. So the typical last frost could fall anywhere from April 4 to 21 and the typical first frost from October 25 to November 7, depending on whether your garden is more like one or the other. Local terrain matters: hillsides, valley floors, water and city heat can change frost dates a lot over a few miles. Treat the dates here as a starting point, and compare with a nearby gardener or your county extension office.
Print a year planner for Philadelphia
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | March 21 | April 4 | April 17 |
| First frost in fall | October 24 | November 7 | November 22 |
The frost-free season between them runs 216 days in a typical year. In 1 year in 10 it is 236 days or longer, and in 1 year in 10 it is 197 days or shorter.
- Hard freeze (28°F): typically last on March 23 and first on November 19. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 17 and first on October 27. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Philadelphia comes between March 21 and April 17, a window of 27 days. That is narrower than at most NOAA stations (the typical window is 31 days), so the typical date is a steadier guide here than in most places.
Among Pennsylvania's 160 NOAA stations with a frost every year, 97 percent have their typical last frost later than Philadelphia does.
Planting calendar for Philadelphia
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 17 to February 14 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| January 31 to February 28 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| February | ||
| February 14 to March 7 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| February 21 to March 7 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| February 28 to March 14 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| March | ||
| March 7 to 21 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 7 to 21 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| March 21 to April 4 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| March 21 to April 4 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| April | ||
| April 4 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| April 18 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| April 18 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 12 to 26 | Cabbage for fall Start seeds | set the plants out by July 31 |
| July | ||
| July 2 to 16 | Broccoli for fall Start seeds | set the plants out by August 20 |
| August | ||
| August 11 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 15 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| August 16 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 20 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| August 21 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 25 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 4 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September 14 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| September 24 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 24 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| November | ||
| November 26 to December 3 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 13 days later. That plans around April 17, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Philadelphia Ne Airport (station USW00094732), 8 miles from the center of Philadelphia. It sits at about the same elevation, 100 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
Our ZIP code lookup matches these 15 ZIP codes to the same station, so they get the same dates: 18966, 19006, 19012, 19020, 19027, 19053, 19111, 19114, 19115, 19116, 19126, 19136, 19149, 19152, 19154. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Trenton, New Jersey: last frost around April 10, first frost around November 1 (25 miles away)
- Wilmington, Delaware: last frost around April 7, first frost around November 1 (30 miles away)
- Allentown, Pennsylvania: last frost around April 20, first frost around October 24 (45 miles away)
See frost dates across Pennsylvania, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.