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