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 18. 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 19, so we don't dare plant that early. We wait a few days and by April 30 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° | Mar 21 | Mar 12 | Mar 6 | Mar 1 | Feb 24 | Feb 19 | Feb 13 | Feb 7 | Jan 29 |
Last 20° | Mar 29 | Mar 22 | Mar 18 | Mar 14 | Mar 10 | Mar 7 | Mar 3 | Feb 26 | Feb 20 |
Last 24° | Apr 7 | Apr 3 | Mar 31 | Mar 29 | Mar 27 | Mar 24 | Mar 22 | Mar 19 | Mar 15 |
Last 28° | Apr 18 | Apr 14 | Apr 10 | Apr 7 | Apr 4 | Apr 1 | Mar 29 | Mar 26 | Mar 21 |
Last 32° | May 4 | Apr 28 | Apr 25 | Apr 21 | Apr 18 | Apr 15 | Apr 12 | Apr 8 | Apr 3 |
Last 36° | May 18 | May 12 | May 7 | May 4 | Apr 30 | Apr 27 | Apr 23 | Apr 19 | Apr 13 |
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 9 | Nov 16 | Nov 21 | Nov 26 | Nov 30 | Dec 4 | Dec 9 | Dec 14 | Dec 21 |
First 20° | Nov 1 | Nov 7 | Nov 12 | Nov 16 | Nov 19 | Nov 23 | Nov 27 | Dec 2 | Dec 8 |
First 24° | Oct 21 | Oct 27 | Oct 31 | Nov 4 | Nov 8 | Nov 11 | Nov 15 | Nov 20 | Nov 26 |
First 28° | Oct 10 | Oct 17 | Oct 22 | Oct 26 | Oct 30 | Nov 3 | Nov 7 | Nov 12 | Nov 19 |
First 32° | Sep 27 | Oct 3 | Oct 8 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 26 | Nov 1 |
First 36° | Sep 19 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 11 | Oct 16 |
Now that you know your frost dates, use our Garden Planting Calendar for Lebanon, MO 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.