Frost Dates: First and last frost dates for Rockford Ap, 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 26.
- There is a 50% chance of being hit by a 32° frost starting around October 6
- 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 7 | Nov 12 | Nov 16 | Nov 19 | Nov 22 | Nov 25 | Nov 28 | Dec 2 | Dec 7 |
First 20° | Oct 26 | Oct 31 | Nov 4 | Nov 7 | Nov 10 | Nov 13 | Nov 16 | Nov 20 | Nov 25 |
First 24° | Oct 15 | Oct 21 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 6 | Nov 10 | Nov 15 |
First 28° | Oct 1 | Oct 6 | Oct 11 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 29 | Nov 4 |
First 32° | Sep 21 | Sep 26 | Sep 30 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 16 | Oct 21 |
First 36° | Sep 18 | Sep 22 | Sep 25 | Sep 27 | 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 May 3, 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 8 | Apr 1 | Mar 27 | Mar 23 | Mar 19 | Mar 15 | Mar 11 | Mar 6 | Feb 28 |
Last 20° | Apr 12 | Apr 8 | Apr 4 | Apr 1 | Mar 30 | Mar 27 | Mar 24 | Mar 21 | Mar 16 |
Last 24° | Apr 18 | Apr 15 | Apr 12 | Apr 10 | Apr 8 | Apr 6 | Apr 4 | Apr 2 | Mar 30 |
Last 28° | Apr 27 | Apr 23 | Apr 19 | Apr 17 | Apr 14 | Apr 12 | Apr 9 | Apr 6 | Apr 2 |
Last 32° | May 14 | May 10 | May 6 | May 3 | Apr 30 | Apr 27 | Apr 24 | Apr 21 | Apr 16 |
Last 36° | May 26 | May 22 | May 18 | May 15 | May 12 | May 9 | May 6 | May 3 | Apr 28 |
Data is provided by the NOAA National Centers for Environmental Information.