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 31. 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 5, so we don't dare plant that early. We wait a few days and by May 15 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. If conditions change and a surprise frost does threaten, there's always things you can do to protect plants from frost.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
Last 16° | Apr 3 | Mar 28 | Mar 24 | Mar 20 | Mar 16 | Mar 13 | Mar 9 | Mar 5 | Feb 27 |
Last 20° | Apr 18 | Apr 11 | Apr 7 | Apr 3 | Mar 30 | Mar 27 | Mar 23 | Mar 19 | Mar 12 |
Last 24° | Apr 24 | Apr 19 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Apr 1 | Mar 27 |
Last 28° | May 5 | May 1 | Apr 28 | Apr 25 | Apr 23 | Apr 20 | Apr 18 | Apr 15 | Apr 10 |
Last 32° | May 23 | May 17 | May 13 | May 9 | May 6 | May 2 | Apr 28 | Apr 24 | Apr 18 |
Last 36° | May 31 | May 25 | May 22 | May 18 | May 15 | May 12 | May 9 | May 5 | Apr 30 |
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
First 16° | Nov 13 | Nov 20 | Nov 25 | Nov 29 | Dec 3 | Dec 6 | Dec 10 | Dec 15 | Dec 22 |
First 20° | Nov 3 | Nov 8 | Nov 11 | Nov 14 | Nov 17 | Nov 19 | Nov 22 | Nov 25 | Nov 30 |
First 24° | Oct 18 | Oct 23 | Oct 27 | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 17 |
First 28° | Oct 5 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 4 |
First 32° | Sep 23 | Sep 28 | Oct 1 | Oct 4 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 20 |
First 36° | Sep 15 | Sep 18 | Sep 21 | Sep 23 | Sep 26 | Sep 28 | Sep 30 | Oct 3 | Oct 6 |
Now that you know your frost dates, use our Garden Planting Calendar for Millersburg, OH to know when to sow and transplant your various vegetable plants!
Data is provided by the NOAA National Centers for Environmental Information. Photography by Garden.org member TBGDN.