Frost Dates: First and last frost dates for Moose, WY

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 30. 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 July 8, so we don't dare plant that early. We wait a few days and by July 17 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. If conditions change and a surprise frost does threaten, there's always things you can do to protect plants from frost.

In the Spring
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
Last 16° May 8 May 3 Apr 29 Apr 27 Apr 24 Apr 21 Apr 18 Apr 15 Apr 10
Last 20° May 19 May 14 May 10 May 7 May 4 May 2 Apr 28 Apr 25 Apr 20
Last 24° Jun 6 May 31 May 27 May 23 May 19 May 16 May 12 May 7 May 1
Last 28° Jul 5 Jun 27 Jun 22 Jun 17 Jun 13 Jun 9 Jun 4 May 29 May 22
Last 32° Jul 19 Jul 15 Jul 11 Jul 8 Jul 5 Jul 3 Jun 30 Jun 26 Jun 21
Last 36° Jul 30 Jul 26 Jul 22 Jul 20 Jul 17 Jul 14 Jul 12 Jul 8 Jul 4

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Moose, WY 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 6, and by September 5 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 12.
  2. There is a 50% chance of being hit by a 32° frost starting around August 24
  3. You have a 80% chance of seeing 32° by September 5
  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° Sep 25 Sep 30 Oct 5 Oct 8 Oct 11 Oct 15 Oct 18 Oct 22 Oct 28
First 20° Sep 15 Sep 20 Sep 24 Sep 27 Sep 29 Oct 2 Oct 5 Oct 9 Oct 14
First 24° Sep 6 Sep 11 Sep 14 Sep 17 Sep 20 Sep 23 Sep 25 Sep 29 Oct 4
First 28° Aug 18 Aug 24 Aug 28 Sep 1 Sep 4 Sep 8 Sep 12 Sep 16 Sep 22
First 32° Aug 6 Aug 12 Aug 17 Aug 20 Aug 24 Aug 28 Sep 1 Sep 5 Sep 11
First 36° Jul 31 Aug 3 Aug 5 Aug 8 Aug 10 Aug 12 Aug 15 Aug 18 Aug 22

Now that you know your frost dates, use our Garden Planting Calendar for Moose, WY to know when to sow and transplant your various vegetable plants!

Data is provided by the NOAA National Centers for Environmental Information. Photography by Garden.org member TBGDN.

Sponsored by Victory Seed Company
Victory Seed Company The Victory Seed Company is family owned and operated, working to help fellow gardeners succeed by selling popular vegetable, herb and flower seeds. Since the 1990s they have been heavily involved with the preservation of rare, open-pollinated, heirloom seeds. Visit them at www.VictorySeeds.com.
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