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