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