Frost Dates: First and last frost dates for Carroll, IA
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 19.
- There is a 50% chance of being hit by a 32° frost starting around September 30
- You have a 80% chance of seeing 32° by October 11
- 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 28 | Nov 3 | Nov 7 | Nov 10 | Nov 14 | Nov 17 | Nov 21 | Nov 25 | Dec 1 |
First 20° | Oct 17 | Oct 23 | Oct 27 | Oct 31 | Nov 3 | Nov 7 | Nov 10 | Nov 15 | Nov 21 |
First 24° | Oct 10 | Oct 15 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 4 | Nov 9 |
First 28° | Sep 24 | Sep 30 | Oct 4 | Oct 8 | Oct 12 | Oct 16 | Oct 20 | Oct 24 | Oct 30 |
First 32° | Sep 14 | Sep 19 | Sep 24 | Sep 27 | Sep 30 | Oct 4 | Oct 7 | Oct 11 | Oct 17 |
First 36° | Sep 11 | Sep 15 | Sep 18 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Sep 30 | Oct 5 |
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 24. 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 10 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 4 | Mar 30 | Mar 27 | Mar 24 | Mar 22 | Mar 19 | Mar 16 | Mar 13 | Mar 8 |
Last 20° | Apr 16 | Apr 11 | Apr 7 | Apr 4 | Apr 2 | Mar 30 | Mar 27 | Mar 23 | Mar 18 |
Last 24° | Apr 19 | Apr 15 | Apr 13 | Apr 10 | Apr 8 | Apr 6 | Apr 4 | Apr 1 | Mar 28 |
Last 28° | May 5 | Apr 29 | Apr 26 | Apr 22 | Apr 19 | Apr 16 | Apr 13 | Apr 9 | Apr 4 |
Last 32° | May 15 | May 10 | May 7 | May 4 | May 1 | Apr 28 | Apr 25 | Apr 22 | Apr 17 |
Last 36° | May 24 | May 19 | May 16 | May 13 | May 10 | May 7 | May 5 | May 1 | Apr 26 |
Data is provided by the NOAA National Centers for Environmental Information.