Philadelphia, Pennsylvania, United States

Frost dates for Philadelphia

The full distribution rather than a single date. Every figure below is a percentile of 30 years of daily minimum temperatures at this location, expressed as the date it fell on.

Median last spring frost

14 April

Half of years are later than this. Not a planting date.

Median first autumn frost

2 November

The far end of the outdoor season.

Frost-free season

202 days

Between those two dates in a median year.

Last and first frost by severity

Read a row as: in this fraction of years, the last frost of spring had already happened by this date. The 90% column is the cautious planting date; the 10% column is the gamble.

Light frost — nights at or below 0°C (32°F). Air temperature reaches freezing. Kills basil, beans and unhardened tomatoes; hardy crops shrug it off.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	3 Apr	14 Apr	23 Apr	28 Mar	29 Apr
First of autumn	22 Oct	2 Nov	13 Nov	14 Oct	17 Nov
Frost-free days	224	202	182	every year on record saw this

Moderate frost — nights at or below -2.2°C (28°F). Damages half-hardy plants and most blossom. This is the threshold that decides a fruit crop.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	25 Mar	2 Apr	14 Apr	22 Mar	19 Apr
First of autumn	4 Nov	11 Nov	24 Nov	30 Oct	6 Dec
Frost-free days	244	223	204	every year on record saw this

Hard frost — nights at or below -4.4°C (24.1°F). Ground freezes and even hardy crops check their growth. Effectively the end of the outdoor year.
Frost	1 year in 10	Median	9 years in 10	Earliest	Latest
Last of spring	7 Mar	24 Mar	5 Apr	22 Feb	11 Apr
First of autumn	12 Nov	24 Nov	13 Dec	8 Nov	22 Dec
Frost-free days	281	245	221	every year on record saw this

Dates in the southern hemisphere are computed on a growing year that starts in July, which is why "last of spring" falls where it should rather than in the middle of the calendar.

Chance of frost, week by week

Chance of at least one air frost during each week of the year, measured across the full record. The flat stretch in the middle is your frost-free season.

Temperature through the year

Mean monthly temperature across the record. Months shown in blue average at least one air frost.

Monthly means and average number of frost nights.
Month	Mean low	Mean high	Frost nights
January	-4.8°C	3.8°C	26.1
February	-4.1°C	5.4°C	23.6
March	-0.6°C	10.3°C	18.6
April	4.6°C	16.7°C	3.7
May	10.5°C	21.9°C	0
June	15.9°C	26.7°C	0
July	19.3°C	29.9°C	0
August	18.7°C	29.5°C	0
September	14.8°C	26.1°C	0
October	8.2°C	19.5°C	0.6
November	2°C	12.5°C	11
December	-2.1°C	6.6°C	22.7

Turn these dates into a planting calendar →

Nearby

Compare with places close by

Brooklyn Zone 8a 129 km Last frost 29 Mar First 2 Dec New York City Zone 8a 130 km Last frost 29 Mar First 2 Dec Manhattan Zone 7a 137 km Last frost 15 Apr First 4 Nov Queens Zone 8a 139 km Last frost 29 Mar First 2 Dec The Bronx Zone 7a 148 km Last frost 15 Apr First 4 Nov