Frost Dates: First and last frost dates for washington is, wi
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
- You have a small 20% chance of getting 32° by September 26.
- There is a 50% chance of being hit by a 32° frost starting around October 8
- You have a 80% chance of seeing 32° by October 19
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
First 16° | Nov 7 | Nov 14 | Nov 19 | Nov 23 | Nov 27 | Nov 30 | Dec 4 | Dec 9 | Dec 16 |
First 20° | Oct 30 | Nov 5 | Nov 9 | Nov 13 | Nov 16 | Nov 20 | Nov 23 | Nov 28 | Dec 3 |
First 24° | Oct 17 | Oct 23 | Oct 28 | Oct 31 | Nov 4 | Nov 7 | Nov 11 | Nov 15 | Nov 21 |
First 28° | Oct 1 | Oct 7 | Oct 11 | Oct 15 | Oct 19 | Oct 22 | Oct 26 | Oct 30 | Nov 5 |
First 32° | Sep 20 | Sep 26 | Sep 30 | Oct 4 | Oct 8 | Oct 11 | Oct 15 | Oct 19 | Oct 25 |
First 36° | Sep 8 | Sep 15 | Sep 19 | Sep 23 | Sep 27 | Sep 30 | Oct 4 | Oct 8 | Oct 15 |
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 June 21. 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 22, so we don't dare plant that early. We wait a few days and by June 3 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.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
Last 16° | Apr 13 | Apr 8 | Apr 4 | Apr 1 | Mar 29 | Mar 26 | Mar 23 | Mar 20 | Mar 15 |
Last 20° | Apr 22 | Apr 17 | Apr 14 | Apr 11 | Apr 8 | Apr 5 | Apr 2 | Mar 30 | Mar 25 |
Last 24° | May 7 | May 2 | Apr 29 | Apr 26 | Apr 23 | Apr 21 | Apr 18 | Apr 15 | Apr 10 |
Last 28° | May 19 | May 15 | May 11 | May 8 | May 5 | May 3 | Apr 30 | Apr 26 | Apr 21 |
Last 32° | Jun 4 | May 30 | May 26 | May 23 | May 20 | May 17 | May 14 | May 10 | May 5 |
Last 36° | Jun 21 | Jun 15 | Jun 10 | Jun 6 | Jun 3 | May 30 | May 26 | May 22 | May 15 |
Data is provided by the NOAA National Centers for Environmental Information.