Frost Dates: First and last frost dates for Philadelphia, PA

How to read these charts for the spring
As the growing season approaches, the days get longer, the weather begins to warm up, and the nights start being less cold. You're still getting frost, but the chance of nightly frosts gets less and less with each passing day. Eventually, the frost stops, and this is when your tender plants are fully safe. So, how do you plan for this? The probabilities on this page help you assess your risk of frost on any given day.

What's a safe temperature for tender plants? When the nightly temperature falls, frost can form, even above 32°, because the air is colder high above the ground and the frost can form up there and then fall down onto your garden and do some damage, even if it's 36° on the ground. So many factors come into play, including wind, concrete, houses, trees and other structures, etc etc etc. Because of all this, you might want to consider 36° as "the danger zone".

In your average springtime, you have a 90% chance that there will be no 36° nights by April 27. In other words, you can pretty much count on being safe from frost by that day. But we want to get those tomatoes in the ground as soon as possible, right? We see that there's still an 80% chance of 36° on April 7, so we don't dare plant that early. We wait a few days and by April 15 we are at the 50/50 point. At this point, we are close and we can start watching the weather forecast. If the upcoming week's forecast doesn't show below 40°, then it's probably okay to risk planting out your plants.

In the Spring
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
Last 16° Mar 13 Mar 5 Feb 27 Feb 22 Feb 18 Feb 13 Feb 8 Feb 3 Jan 26
Last 20° Mar 24 Mar 18 Mar 14 Mar 10 Mar 6 Mar 3 Feb 27 Feb 23 Feb 16
Last 24° Mar 30 Mar 25 Mar 21 Mar 18 Mar 15 Mar 12 Mar 9 Mar 5 Feb 28
Last 28° Apr 9 Apr 4 Apr 1 Mar 29 Mar 26 Mar 23 Mar 20 Mar 16 Mar 11
Last 32° Apr 19 Apr 14 Apr 11 Apr 8 Apr 6 Apr 3 Apr 1 Mar 29 Mar 24
Last 36° Apr 27 Apr 23 Apr 20 Apr 18 Apr 15 Apr 13 Apr 10 Apr 7 Apr 3

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Philadelphia, PA start to go down, and therefore every day that goes by increases the chance that you'll get frost. Your risk of frost really begins around October 20, and by November 13 you're almost certain to have received at least one frost event.

The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:

  1. You have a small 20% chance of getting 32° by October 25.
  2. There is a 50% chance of being hit by a 32° frost starting around November 4
  3. You have a 80% chance of seeing 32° by November 13
  4. Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
In the Fall
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
First 16° Dec 10 Dec 17 Dec 22 Dec 27 Dec 31 Jan 4 Jan 8 Jan 13 Jan 21
First 20° Nov 28 Dec 4 Dec 8 Dec 12 Dec 15 Dec 18 Dec 21 Dec 26 Dec 31
First 24° Nov 16 Nov 22 Nov 25 Nov 29 Dec 2 Dec 5 Dec 8 Dec 12 Dec 17
First 28° Nov 3 Nov 9 Nov 12 Nov 16 Nov 19 Nov 22 Nov 25 Nov 29 Dec 5
First 32° Oct 20 Oct 25 Oct 29 Nov 1 Nov 4 Nov 7 Nov 10 Nov 13 Nov 18
First 36° Oct 12 Oct 17 Oct 20 Oct 23 Oct 26 Oct 29 Nov 1 Nov 4 Nov 9

Frost Dates for other nearby locations
  • Moorestown, NJ
  • Glassboro, NJ
  • Norristown, PA
  • Neshaminy Falls, PA
  • Marcus Hook, PA
  • Phoenixville, PA
  • Graterford, PA
  • Indian Mills, NJ
  • Woodstown Pittsgrov, NJ
  • Lambertville, NJ

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    • Data is provided by the NOAA National Centers for Environmental Information.