Frost dates for Philadelphia International Airport, Pennsylvania
Half of years have their last spring frost by April 2, but 1 year in 10 still frosts after April 13.
A frost date is really a percentile from 30 years of records at a nearby weather station: in about half of years a frost still comes after the median date. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
How often a frost still comes on or after each date.
- 1 year in 10
- April 13
- 1 year in 5
- April 8
- 3 years in 10
- April 6
- 2 years in 5
- April 3
- Half of years (the median)
- April 2
First fall freeze
How often the first freeze comes on or before each date.
- 1 year in 10
- October 30
- 1 year in 5
- November 2
- 3 years in 10
- November 5
- 2 years in 5
- November 8
- Half of years (the median)
- November 10
- Growing season
- about 224 days
- Hardiness zones nearby
- 7b, 8a
- Summer days
- a usual high of about 30 °C86 °F
- Lettuce and spinach run to seed
- June to September, in hot, long days (how we know)
Summer and rain
A growing garden needs about 25 mm1 in of water a week, rain and watering together. Here is what a normal month brings.
Month by month
- January
- high ~5 °C41 °F · low ~-3 °C26 °F · rain ~80 mm3.1 in
- February
- high ~7 °C44 °F · low ~-2 °C28 °F · rain ~70 mm2.7 in
- March
- high ~12 °C53 °F · low ~1 °C34 °F · rain ~101 mm4 in
- April
- high ~18 °C65 °F · low ~7 °C44 °F · rain ~88 mm3.5 in
- May
- high ~24 °C74 °F · low ~12 °C54 °F · rain ~85 mm3.3 in
- June
- high ~28 °C83 °F · low ~18 °C64 °F · rain ~103 mm4 in
- July
- high ~31 °C88 °F · low ~21 °C70 °F · rain ~111 mm4.4 in
- August
- high ~30 °C86 °F · low ~20 °C68 °F · rain ~109 mm4.3 in
- September
- high ~26 °C79 °F · low ~16 °C61 °F · rain ~112 mm4.4 in
- October
- high ~20 °C67 °F · low ~10 °C49 °F · rain ~88 mm3.5 in
- November
- high ~13 °C56 °F · low ~4 °C39 °F · rain ~74 mm2.9 in
- December
- high ~8 °C46 °F · low ~0 °C31 °F · rain ~101 mm4 in
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, the Philadelphia International Airport station (listed by NOAA as Philadelphia Intl Ap, USW00013739), at 39.87, -75.23. These are that station’s own records, unshifted. The further your garden is from it, the less exactly they describe your ground. The planner finds the nearest station to your garden and lowers its confidence with distance, so no number is presented as if it were measured in your garden.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a few hundred feet away does not. No table can know that about your garden. A few seasons of your own logged frosts can.
ZIP codes nearest this station
08020, 08027, 08031, 08056, 08061, 08063, 08066, 08086, 08093, 08096, 19018, 19023…
+17 moreShow fewer
19026, 19029, 19032, 19033, 19036, 19043, 19064, 19070, 19074, 19076, 19078, 19079, 19112, 19113, 19142, 19145, 19153.
Nearby stations
The nearest stations and how their last-frost dates compare. Together they show how frost varies across your area.
- Phila Franklin Inst, PA, last frost by March 30
- Willow Grove Naval Air Station, PA, last frost by April 11
- Indian Mills 2 W, NJ, last frost by April 28
- Newark Ag Farm, DE, last frost by April 7
- Millville Municipal Airport, NJ, last frost by April 24
- Trenton State College, NJ, last frost by April 17
Other stations in Pennsylvania.
- Rodale Rsch Center, PA, last frost by April 26
- Lancaster Airport, PA, last frost by April 18
- Lehighton 1 SSW, PA, last frost by April 21
- Mahanoy City 2 N, PA, last frost by April 30
- Middletown Harrisburg International Airport, PA, last frost by April 9
- Mt Pocono Mountains Airport, PA, last frost by May 6
- Wilkes-Barre International Airport, PA, last frost by April 23
- Carlisle Wtp, PA, last frost by April 23
When do I plant? · Where the dates come from
More ways Milpa can help
When do I plant? · What grows well together? · Plan my garden · What can I plant now? · Something wrong in the garden? · Keep a garden diary · Heard a tip?