Frost Dates: First and last frost dates for Brothers, 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 August 2, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 22, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before July 15, 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° May 23 May 14 May 8 May 2 Apr 27 Apr 22 Apr 16 Apr 10 Apr 1
Last 20° Jun 12 Jun 3 May 28 May 23 May 18 May 14 May 8 May 2 Apr 24
Last 24° Jul 8 Jun 29 Jun 22 Jun 17 Jun 12 Jun 6 Jun 1 May 25 May 16
Last 28° Jul 24 Jul 17 Jul 12 Jul 7 Jul 3 Jun 29 Jun 25 Jun 20 Jun 12
Last 32° Jul 29 Jul 23 Jul 19 Jul 16 Jul 12 Jul 9 Jul 5 Jul 1 Jun 26
Last 36° Aug 2 Jul 29 Jul 26 Jul 24 Jul 22 Jul 20 Jul 17 Jul 15 Jul 11

ℹ️ How to read these charts for the fall

As summer ends in Brothers, 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 5, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By August 17, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By August 29, 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 August 29 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° Sep 21 Sep 28 Oct 4 Oct 8 Oct 13 Oct 17 Oct 22 Oct 27 Nov 4
First 20° Sep 8 Sep 15 Sep 20 Sep 25 Sep 29 Oct 3 Oct 8 Oct 13 Oct 20
First 24° Aug 25 Sep 1 Sep 7 Sep 11 Sep 15 Sep 20 Sep 24 Sep 29 Oct 7
First 28° Aug 5 Aug 14 Aug 19 Aug 24 Aug 29 Sep 3 Sep 8 Sep 13 Sep 22
First 32° Jul 31 Aug 5 Aug 9 Aug 13 Aug 17 Aug 20 Aug 24 Aug 29 Sep 4
First 36° Jul 29 Aug 2 Aug 6 Aug 9 Aug 11 Aug 14 Aug 17 Aug 20 Aug 25

📍 Frost Dates for other nearby locations

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