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