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

ℹ️ How to read these charts for the spring

As spring unfolds, the risk of frost gradually decreases each day until your tender plants are finally safe. The probabilities shown in the chart help you make smart decisions about when to plant.

While frost typically forms at 32°F, tender plants can be damaged even when temperatures are slightly higher. Air temperatures are often measured several feet above the ground, but temperatures at plant level can be several degrees colder. Protected areas like porches help by blocking radiational cooling. Given these variables, we consider 36°F the "caution zone" for frost-sensitive plants.

Key dates for your spring planting:

  • By July 18, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around June 30, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before June 18, there's still an 80% risk of frost — too early for tomatoes and other tender plants unless you're prepared to protect them

If the 10-day forecast shows no temperatures below 40°F, you might safely plant earlier than the above dates suggest. Many gardeners watch for this weather window to get a head start on the growing season.

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

ℹ️ How to read these charts for the fall

As summer ends in Malheur Refuge Hq, OR, nighttime temperatures begin to drop, and your risk of frost increases with each passing day. Knowing when to expect frost helps you harvest sensitive crops and extend your growing season with protection methods.

The chart below shows the probability of experiencing specific temperatures on various dates. Here's what this means for your garden:

1
Early warning: Around August 27, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 8, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By September 20, there's an 80% chance of seeing 32°F — most tender plants will be damaged without protection
4
Another perspective: You have only a 1 in 5 chance of making it past September 20 without a freezing night

These probabilities help you time your end-of-season harvests and know when to apply protective measures like row covers, cloches, or cold frames to extend your harvest.

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

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