Frost Dates: First and last frost dates for Lancaster, 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 May 17. 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 13, so we don't dare plant that early. We wait a few days and by April 27 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 22 Mar 12 Mar 5 Feb 27 Feb 22 Feb 16 Feb 10 Feb 3 Jan 25
Last 20° Mar 25 Mar 19 Mar 14 Mar 10 Mar 6 Mar 2 Feb 26 Feb 22 Feb 15
Last 24° Apr 4 Mar 29 Mar 24 Mar 19 Mar 15 Mar 11 Mar 7 Mar 2 Feb 23
Last 28° Apr 17 Apr 11 Apr 6 Apr 3 Mar 30 Mar 27 Mar 23 Mar 19 Mar 13
Last 32° May 1 Apr 25 Apr 21 Apr 17 Apr 14 Apr 11 Apr 7 Apr 3 Mar 28
Last 36° May 17 May 10 May 5 May 1 Apr 27 Apr 22 Apr 18 Apr 13 Apr 6

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Lancaster, 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 6, and by October 30 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 11.
  2. There is a 50% chance of being hit by a 32° frost starting around October 21
  3. You have a 80% chance of seeing 32° by October 30
  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 30 Dec 6 Dec 11 Dec 15 Dec 18 Dec 22 Dec 26 Dec 31 Jan 6
First 20° Nov 15 Nov 22 Nov 26 Nov 30 Dec 4 Dec 8 Dec 12 Dec 17 Dec 23
First 24° Oct 30 Nov 5 Nov 10 Nov 14 Nov 18 Nov 22 Nov 26 Dec 1 Dec 8
First 28° Oct 12 Oct 19 Oct 23 Oct 27 Oct 31 Nov 4 Nov 8 Nov 12 Nov 19
First 32° Oct 6 Oct 11 Oct 15 Oct 18 Oct 21 Oct 23 Oct 26 Oct 30 Nov 4
First 36° Sep 24 Sep 28 Oct 1 Oct 4 Oct 6 Oct 9 Oct 11 Oct 14 Oct 18

Frost Dates for other nearby locations
  • Landisville, PA
  • Lebanon, PA
  • Conowingo Dam, MD
  • York, PA
  • Aberdeen Phillips Fld, MD
  • Newark Univ Farm, DE
  • West Chester, PA
  • Wilmington New Castle Co Ap, DE
  • Phoenixville, PA
  • Chestertown, MD

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