Frost Dates: First and last frost dates for Graterford, 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 June 1. 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 May 1, so we don't dare plant that early. We wait a few days and by May 14 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 29 Mar 22 Mar 17 Mar 13 Mar 9 Mar 4 Feb 28 Feb 23 Feb 16
Last 20° Apr 11 Apr 3 Mar 28 Mar 24 Mar 19 Mar 15 Mar 10 Mar 5 Feb 25
Last 24° Apr 22 Apr 15 Apr 11 Apr 7 Apr 3 Mar 31 Mar 27 Mar 22 Mar 16
Last 28° May 10 May 2 Apr 27 Apr 22 Apr 18 Apr 13 Apr 9 Apr 3 Mar 26
Last 32° May 24 May 17 May 11 May 7 May 2 Apr 28 Apr 23 Apr 18 Apr 10
Last 36° Jun 1 May 26 May 21 May 17 May 14 May 10 May 6 May 1 Apr 25

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Graterford, 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 September 16, and by October 24 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 September 24.
  2. There is a 50% chance of being hit by a 32° frost starting around October 9
  3. You have a 80% chance of seeing 32° by October 24
  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° Nov 7 Nov 17 Nov 24 Nov 30 Dec 5 Dec 10 Dec 16 Dec 23 Jan 2
First 20° Oct 30 Nov 7 Nov 13 Nov 18 Nov 23 Nov 28 Dec 3 Dec 9 Dec 17
First 24° Oct 7 Oct 17 Oct 24 Oct 30 Nov 5 Nov 11 Nov 17 Nov 24 Dec 4
First 28° Sep 24 Oct 3 Oct 10 Oct 16 Oct 22 Oct 27 Nov 2 Nov 9 Nov 18
First 32° Sep 16 Sep 24 Sep 29 Oct 4 Oct 9 Oct 13 Oct 18 Oct 24 Oct 31
First 36° Sep 8 Sep 15 Sep 20 Sep 24 Sep 28 Oct 2 Oct 6 Oct 11 Oct 18

Frost Dates for other nearby locations
  • Phoenixville, PA
  • Norristown, PA
  • West Chester, PA
  • Marcus Hook, PA
  • Philadelphia, PA
  • Allentown, PA
  • Neshaminy Falls, PA
  • Lambertville, NJ
  • Moorestown, NJ
  • Wilmington New Castle Co Ap, DE

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