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