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