Frost Dates: First and last frost dates for Divide, MT

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 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 June 22, so we don't dare plant that early. We wait a few days and by July 3 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° Apr 21 Apr 16 Apr 12 Apr 9 Apr 6 Apr 3 Mar 30 Mar 27 Mar 21
Last 20° May 7 May 2 Apr 28 Apr 24 Apr 21 Apr 18 Apr 14 Apr 10 Apr 4
Last 24° Jun 3 May 25 May 19 May 14 May 9 May 4 Apr 29 Apr 23 Apr 14
Last 28° Jun 13 Jun 6 May 31 May 27 May 23 May 18 May 14 May 8 May 1
Last 32° Jul 6 Jun 29 Jun 23 Jun 18 Jun 14 Jun 9 Jun 4 May 30 May 22
Last 36° Jul 21 Jul 15 Jul 10 Jul 7 Jul 3 Jun 30 Jun 26 Jun 22 Jun 16

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Divide, MT 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 21, and by September 19 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 27.
  2. There is a 50% chance of being hit by a 32° frost starting around September 7
  3. You have a 80% chance of seeing 32° by September 19
  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 2 Oct 8 Oct 12 Oct 16 Oct 20 Oct 24 Oct 27 Nov 1 Nov 7
First 20° Sep 25 Oct 1 Oct 5 Oct 8 Oct 11 Oct 14 Oct 18 Oct 22 Oct 27
First 24° Sep 14 Sep 20 Sep 24 Sep 28 Oct 1 Oct 4 Oct 8 Oct 12 Oct 18
First 28° Sep 5 Sep 10 Sep 14 Sep 17 Sep 20 Sep 23 Sep 26 Sep 29 Oct 5
First 32° Aug 21 Aug 27 Aug 31 Sep 4 Sep 7 Sep 11 Sep 15 Sep 19 Sep 25
First 36° Aug 12 Aug 17 Aug 21 Aug 24 Aug 27 Aug 30 Sep 2 Sep 6 Sep 11

Frost Dates for other nearby locations
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  • Butte Bert Mooney, MT
  • Twin Bridges, MT
  • Dillion U Of Montana Western, MT
  • Deer Lodge, MT
  • Wisdom, MT
  • Philipsburg Rs, MT
  • Jackson, MT
  • Boulder, MT
  • Drummond Aviation, MT

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