Frost Dates: First and last frost dates for Malheur Refuge Hq, OR

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 18. 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 18, so we don't dare plant that early. We wait a few days and by June 30 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 20 Apr 9 Mar 31 Mar 24 Mar 18 Mar 11 Mar 4 Feb 24 Feb 12
Last 20° May 3 Apr 25 Apr 19 Apr 14 Apr 9 Apr 4 Mar 30 Mar 24 Mar 16
Last 24° May 20 May 14 May 9 May 4 May 1 Apr 27 Apr 22 Apr 17 Apr 11
Last 28° Jun 10 Jun 3 May 29 May 24 May 20 May 16 May 12 May 7 Apr 29
Last 32° Jun 28 Jun 21 Jun 16 Jun 12 Jun 8 Jun 5 Jun 1 May 27 May 20
Last 36° Jul 18 Jul 12 Jul 7 Jul 4 Jun 30 Jun 26 Jun 22 Jun 18 Jun 11

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Malheur Refuge Hq, OR 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 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 27.
  2. There is a 50% chance of being hit by a 32° frost starting around September 8
  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 3 Oct 12 Oct 18 Oct 23 Oct 28 Nov 2 Nov 7 Nov 13 Nov 21
First 20° Sep 27 Oct 4 Oct 10 Oct 14 Oct 19 Oct 23 Oct 28 Nov 2 Nov 10
First 24° Sep 13 Sep 21 Sep 26 Sep 30 Oct 5 Oct 9 Oct 13 Oct 18 Oct 26
First 28° Sep 2 Sep 8 Sep 13 Sep 17 Sep 21 Sep 24 Sep 28 Oct 3 Oct 9
First 32° Aug 21 Aug 27 Sep 1 Sep 4 Sep 8 Sep 11 Sep 15 Sep 20 Sep 26
First 36° Aug 14 Aug 20 Aug 24 Aug 28 Aug 31 Sep 4 Sep 7 Sep 12 Sep 18

Frost Dates for other nearby locations
  • P-ranch South Place, OR
  • O O Rch, OR
  • Riverside, OR
  • Drewsey, OR
  • Seneca, OR
  • Squaw Butte-northern Great Bas, OR
  • Beulah, OR
  • Hart Mtn Refuge, OR
  • Whitehorse Rch, OR
  • John Day, OR

    Or enter a new zipcode:

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