Frost Dates: First and last frost dates for two rivers, 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 October 1.
- There is a 50% chance of being hit by a 32° frost starting around October 11
- You have a 80% chance of seeing 32° by October 22
- 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 8 | Nov 14 | Nov 17 | Nov 21 | Nov 24 | Nov 27 | Nov 30 | Dec 4 | Dec 9 |
First 20° | Oct 31 | Nov 5 | Nov 9 | Nov 12 | Nov 16 | Nov 19 | Nov 22 | Nov 26 | Dec 1 |
First 24° | Oct 27 | Oct 31 | Nov 3 | Nov 6 | Nov 8 | Nov 11 | Nov 13 | Nov 16 | Nov 20 |
First 28° | Oct 13 | Oct 18 | Oct 22 | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 8 | Nov 13 |
First 32° | Sep 25 | Oct 1 | Oct 5 | Oct 8 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 28 |
First 36° | Sep 21 | Sep 25 | Sep 27 | Sep 29 | Oct 2 | Oct 4 | Oct 6 | Oct 9 | Oct 12 |
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 May 27. 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 1, so we don't dare plant that early. We wait a few days and by May 12 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 6 | Mar 31 | Mar 27 | Mar 24 | Mar 21 | Mar 17 | Mar 14 | Mar 10 | Mar 4 |
Last 20° | Apr 10 | Apr 6 | Apr 3 | Mar 31 | Mar 29 | Mar 27 | Mar 25 | Mar 22 | Mar 18 |
Last 24° | Apr 18 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Apr 1 | Mar 29 | Mar 26 | Mar 21 |
Last 28° | May 1 | Apr 26 | Apr 23 | Apr 19 | Apr 16 | Apr 14 | Apr 10 | Apr 7 | Apr 2 |
Last 32° | May 11 | May 7 | May 4 | May 2 | Apr 30 | Apr 27 | Apr 25 | Apr 22 | Apr 18 |
Last 36° | May 27 | May 22 | May 18 | May 15 | May 12 | May 8 | May 5 | May 1 | Apr 26 |
Data is provided by the NOAA National Centers for Environmental Information.