Frost Dates: First and last frost dates for Rockville, MD

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 21. 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 15, so we don't dare plant that early. We wait a few days and by April 29 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 25 Mar 15 Mar 7 Mar 1 Feb 23 Feb 18 Feb 11 Feb 4 Jan 25
Last 20° Mar 31 Mar 25 Mar 20 Mar 16 Mar 12 Mar 8 Mar 4 Feb 27 Feb 21
Last 24° Apr 11 Apr 5 Mar 31 Mar 27 Mar 24 Mar 20 Mar 16 Mar 12 Mar 6
Last 28° Apr 23 Apr 16 Apr 12 Apr 8 Apr 4 Mar 31 Mar 27 Mar 23 Mar 17
Last 32° May 7 Apr 30 Apr 25 Apr 20 Apr 16 Apr 12 Apr 8 Apr 2 Mar 26
Last 36° May 21 May 13 May 8 May 3 Apr 29 Apr 25 Apr 20 Apr 15 Apr 7

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Rockville, MD 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 3, and by November 3 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 9.
  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 November 3
  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 24 Dec 2 Dec 7 Dec 12 Dec 16 Dec 20 Dec 25 Dec 30 Jan 6
First 20° Nov 6 Nov 15 Nov 21 Nov 26 Dec 1 Dec 6 Dec 12 Dec 18 Dec 27
First 24° Oct 21 Oct 30 Nov 6 Nov 12 Nov 17 Nov 23 Nov 28 Dec 5 Dec 15
First 28° Oct 12 Oct 19 Oct 24 Oct 28 Nov 1 Nov 5 Nov 9 Nov 14 Nov 21
First 32° Oct 3 Oct 9 Oct 14 Oct 18 Oct 21 Oct 25 Oct 29 Nov 3 Nov 9
First 36° Sep 23 Sep 29 Oct 3 Oct 7 Oct 10 Oct 14 Oct 17 Oct 22 Oct 28

Frost Dates for other nearby locations
  • Dalecarlia Rsvr, MD
  • Vienna, VA
  • Beltsville, MD
  • Natl Arboretum Dc, MD
  • Laurel, MD
  • Washington Reagan, VA
  • Clarksville, MD
  • Washgtn Dulles, VA
  • Glenn Dale Bell Stn, MD
  • Frederick Police Brks, MD

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