Frost Dates: First and last frost dates for Howard Prairie Dam, 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 24, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 6, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before June 24, 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 7 Mar 30 Mar 23 Mar 18 Mar 13 Mar 8 Mar 3 Feb 25 Feb 16
Last 20° Apr 20 Apr 11 Apr 4 Mar 30 Mar 25 Mar 19 Mar 14 Mar 7 Feb 27
Last 24° May 13 May 4 Apr 28 Apr 23 Apr 18 Apr 13 Apr 8 Apr 1 Mar 24
Last 28° Jun 6 May 30 May 25 May 21 May 17 May 13 May 9 May 4 Apr 27
Last 32° Jul 7 Jun 30 Jun 26 Jun 22 Jun 18 Jun 14 Jun 10 Jun 5 May 30
Last 36° Jul 24 Jul 18 Jul 13 Jul 9 Jul 6 Jul 2 Jun 28 Jun 24 Jun 18

ℹ️ How to read these charts for the fall

As summer ends in Howard Prairie Dam, 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 September 3, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 15, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By September 28, 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 28 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 25 Nov 6 Nov 14 Nov 21 Nov 28 Dec 5 Dec 12 Dec 20 Jan 1
First 20° Oct 26 Nov 2 Nov 6 Nov 10 Nov 14 Nov 18 Nov 22 Nov 27 Dec 3
First 24° Oct 13 Oct 20 Oct 24 Oct 28 Nov 1 Nov 5 Nov 9 Nov 13 Nov 20
First 28° Sep 14 Sep 21 Sep 26 Sep 30 Oct 4 Oct 8 Oct 13 Oct 18 Oct 25
First 32° Aug 28 Sep 3 Sep 8 Sep 12 Sep 15 Sep 19 Sep 23 Sep 28 Oct 4
First 36° Aug 5 Aug 12 Aug 17 Aug 22 Aug 26 Aug 30 Sep 3 Sep 8 Sep 15

📍 Frost Dates for other nearby locations

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