Frost Dates: First and last frost dates for Alkali Lake, 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 31, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 20, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before July 13, 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 9 Apr 29 Apr 20 Apr 12 Apr 4 Mar 27 Mar 17 Mar 3
Last 20° Jun 12 Jun 2 May 26 May 20 May 14 May 9 May 3 Apr 25 Apr 16
Last 24° Jul 9 Jun 29 Jun 23 Jun 17 Jun 12 Jun 7 Jun 1 May 25 May 16
Last 28° Jul 20 Jul 13 Jul 8 Jul 4 Jun 30 Jun 26 Jun 22 Jun 17 Jun 10
Last 32° Jul 27 Jul 21 Jul 17 Jul 13 Jul 10 Jul 7 Jul 3 Jun 29 Jun 23
Last 36° Jul 31 Jul 27 Jul 25 Jul 22 Jul 20 Jul 18 Jul 16 Jul 13 Jul 9

ℹ️ How to read these charts for the fall

As summer ends in Alkali Lake, 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 7, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By August 16, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By August 26, 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 26 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 26 Oct 3 Oct 9 Oct 13 Oct 18 Oct 22 Oct 27 Nov 1 Nov 8
First 20° Sep 4 Sep 12 Sep 19 Sep 24 Sep 29 Oct 4 Oct 9 Oct 16 Oct 24
First 24° Aug 22 Aug 30 Sep 5 Sep 10 Sep 14 Sep 19 Sep 24 Sep 29 Oct 7
First 28° Aug 5 Aug 13 Aug 19 Aug 24 Aug 29 Sep 3 Sep 8 Sep 14 Sep 22
First 32° Aug 1 Aug 7 Aug 10 Aug 13 Aug 16 Aug 19 Aug 22 Aug 26 Aug 31
First 36° Jul 31 Aug 2 Aug 4 Aug 5 Aug 6 Aug 7 Aug 8 Aug 10 Aug 12

📍 Frost Dates for other nearby locations

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