Frost Dates: First and last frost dates for Indianola, 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 24.
- There is a 50% chance of being hit by a 32° frost starting around October 4
- You have a 80% chance of seeing 32° by October 14
- 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 29 | Nov 4 | Nov 9 | Nov 13 | Nov 17 | Nov 21 | Nov 25 | Nov 29 | Dec 6 |
First 20° | Oct 25 | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 22 |
First 24° | Oct 12 | Oct 17 | Oct 21 | Oct 25 | Oct 28 | Oct 31 | Nov 4 | Nov 8 | Nov 13 |
First 28° | Sep 26 | Oct 3 | Oct 7 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 27 | Nov 2 |
First 32° | Sep 19 | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 11 | Oct 14 | Oct 20 |
First 36° | Sep 13 | Sep 17 | Sep 20 | Sep 22 | Sep 25 | Sep 27 | Sep 30 | Oct 3 | Oct 7 |
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 April 25, so we don't dare plant that early. We wait a few days and by May 6 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° | Mar 31 | Mar 25 | Mar 21 | Mar 18 | Mar 15 | Mar 12 | Mar 8 | Mar 5 | Feb 27 |
Last 20° | Apr 10 | Apr 6 | Apr 2 | Mar 30 | Mar 28 | Mar 25 | Mar 22 | Mar 18 | Mar 14 |
Last 24° | Apr 15 | Apr 11 | Apr 8 | Apr 6 | Apr 4 | Apr 2 | Mar 30 | Mar 27 | Mar 23 |
Last 28° | Apr 28 | Apr 23 | Apr 19 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 3 | Mar 29 |
Last 32° | May 9 | May 5 | May 2 | Apr 29 | Apr 27 | Apr 24 | Apr 22 | Apr 19 | Apr 15 |
Last 36° | May 24 | May 18 | May 13 | May 10 | May 6 | May 3 | Apr 29 | Apr 25 | Apr 19 |
Data is provided by the NOAA National Centers for Environmental Information.