Frost Dates: First and last frost dates for Chewelah, WA

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 10. 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 May 27, so we don't dare plant that early. We wait a few days and by June 14 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. If conditions change and a surprise frost does threaten, there's always things you can do to protect plants from frost.

In the Spring
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
Last 16° Mar 15 Mar 8 Mar 2 Feb 26 Feb 21 Feb 17 Feb 12 Feb 7 Jan 30
Last 20° Apr 7 Mar 30 Mar 25 Mar 20 Mar 16 Mar 11 Mar 7 Mar 1 Feb 22
Last 24° Apr 28 Apr 22 Apr 17 Apr 13 Apr 10 Apr 6 Apr 2 Mar 29 Mar 22
Last 28° May 17 May 11 May 7 May 3 Apr 29 Apr 26 Apr 22 Apr 17 Apr 11
Last 32° Jun 3 May 28 May 24 May 20 May 16 May 13 May 9 May 5 Apr 28
Last 36° Jul 10 Jul 1 Jun 24 Jun 19 Jun 14 Jun 8 Jun 3 May 27 May 18

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Chewelah, WA 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 September 3, and by September 27 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 September 8.
  2. There is a 50% chance of being hit by a 32° frost starting around September 17
  3. You have a 80% chance of seeing 32° by September 27
  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 22 Oct 30 Nov 5 Nov 11 Nov 16 Nov 21 Nov 26 Dec 2 Dec 11
First 20° Oct 5 Oct 11 Oct 15 Oct 18 Oct 22 Oct 25 Oct 29 Nov 2 Nov 8
First 24° Sep 24 Sep 30 Oct 4 Oct 8 Oct 12 Oct 15 Oct 19 Oct 23 Oct 29
First 28° Sep 14 Sep 19 Sep 23 Sep 26 Sep 29 Oct 2 Oct 6 Oct 9 Oct 15
First 32° Sep 3 Sep 8 Sep 11 Sep 14 Sep 17 Sep 20 Sep 23 Sep 27 Oct 2
First 36° Aug 23 Aug 27 Aug 31 Sep 3 Sep 6 Sep 9 Sep 12 Sep 15 Sep 20

Now that you know your frost dates, use our Garden Planting Calendar for Chewelah, WA to know when to sow and transplant your various vegetable plants!

Data is provided by the NOAA National Centers for Environmental Information. Photography by Garden.org member TBGDN.

Sponsored by Victory Seed Company
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