When is the last frost in Allentown, PA?

The average (50% probability) last spring frost in Allentown is April 20, based on NOAA 1991–2020 normals. A 1-in-10 risk remains until May 6.

When is the first frost in Allentown?

The average first fall frost in Allentown is October 24, with a growing season of about 184 days.

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Allentown, Pennsylvania frost dates

Average last spring frost: April 20. Average first fall frost: October 24. That gives a growing season of about 184 days. For frost-tender plants, a safer planting date is May 6, after which a freeze happens in only 1 year in 10.

Last frost (50%)

Apr 20

1-in-10 risk after May 6

First frost (50%)

Oct 24

1-in-10 risk before Oct 8

Growing season

184 days

median frost-free days

Hard freeze (28°F)

Apr 5

median last 28°F in spring

Frost risk by date

Chance of frost	Spring: frost after	Fall: frost before
90%	April 6	November 6
70%	April 14	October 31
50%	April 20	October 24
30%	April 26	October 17
10%	May 6	October 8

Read the spring column like this: there is a 10% chance of a 32°F freeze after May 6. These are NOAA probabilities for the Allentown International Airport weather station (USW00014737, elevation 119 m), 1991–2020.

Allentown vegetable planting calendar

Dates count from the 50% last-frost date (April 20). For tomatoes, peppers and other frost-tender crops, waiting until the 10% date (May 6) is the cautious choice.

Crop	Start seeds indoors	Plant out
Beans	Mar 30	Apr 27 (usually sown directly in the garden)
Broccoli	Feb 9	Mar 23
Brussels sprouts	Feb 9	Mar 23
Cabbage	Feb 2	Mar 16
Cauliflower	Feb 23	Apr 6
Sweet corn	Mar 23	Apr 20 (usually sown directly in the garden)
Cucumbers	Apr 6	Apr 27
Kale	Feb 2	Mar 16
Leeks	Jan 5	Mar 16
Lettuce	Mar 2	Apr 6
Melons	Apr 13	May 4
Onions	Dec 29	Mar 9 (from seed; sets and transplants go out at the same time)
Peas	Feb 23	Mar 23 (usually sown directly in the garden)
Peppers	Mar 9	May 4
Squash	Apr 13	May 4
Tomatoes	Feb 23	Apr 20

Offsets from Oregon State University Extension's seed-starting table. "Plant out" means transplant, or sow directly for crops usually grown from seed.

Fall frost and season extension

The first fall freeze usually arrives around October 24. There's a 1-in-10 chance it comes before October 8. Harvest tender crops such as basil, tomatoes, peppers and squash before then, or cover them on cold nights. Cool-season crops like kale, cabbage and Brussels sprouts handle light frost, and often taste sweeter after it. A hard freeze (28°F) typically comes around November 4.

Nearby cities

City	Last frost (50%)	First frost (50%)	Distance
Philadelphia, PA	Apr 2	Nov 10	~89 km
Newark, NJ	Apr 2	Nov 10	~108 km
Harrisburg, PA	Apr 9	Nov 2	~122 km
New York, NY	Apr 2	Nov 14	~142 km
Baltimore, MD	Apr 10	Oct 31	~195 km
Washington, DC	Mar 24	Nov 18	~241 km

More: all Pennsylvania frost dates