Frost Dates: First and last frost dates for green mt dam, co

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 July 28. 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 June 19, so we don't dare plant that early. We wait a few days and by July 4 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° May 2 Apr 26 Apr 23 Apr 19 Apr 16 Apr 13 Apr 10 Apr 7 Apr 1
Last 20° May 9 May 4 Apr 30 Apr 26 Apr 23 Apr 20 Apr 16 Apr 12 Apr 6
Last 24° Jun 9 May 30 May 23 May 16 May 11 May 5 Apr 29 Apr 22 Apr 12
Last 28° Jun 30 Jun 18 Jun 9 Jun 2 May 26 May 19 May 12 May 3 Apr 21
Last 32° Jul 13 Jul 4 Jun 27 Jun 22 Jun 16 Jun 11 Jun 6 May 30 May 21
Last 36° Jul 28 Jul 20 Jul 14 Jul 9 Jul 4 Jun 30 Jun 25 Jun 19 Jun 11

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for green mt dam, co 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 August 14, and by September 20 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 August 22.
  2. There is a 50% chance of being hit by a 32° frost starting around September 5
  3. You have a 80% chance of seeing 32° by September 20
  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° Oct 6 Oct 12 Oct 16 Oct 20 Oct 23 Oct 27 Oct 31 Nov 4 Nov 10
First 20° Sep 22 Sep 29 Oct 3 Oct 7 Oct 11 Oct 14 Oct 18 Oct 23 Oct 29
First 24° Sep 8 Sep 14 Sep 19 Sep 23 Sep 27 Oct 1 Oct 5 Oct 10 Oct 17
First 28° Aug 22 Aug 30 Sep 4 Sep 9 Sep 13 Sep 17 Sep 22 Sep 27 Oct 5
First 32° Aug 14 Aug 22 Aug 27 Sep 1 Sep 5 Sep 10 Sep 15 Sep 20 Sep 28
First 36° Aug 1 Aug 8 Aug 13 Aug 17 Aug 21 Aug 24 Aug 29 Sep 2 Sep 9

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