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 28 | Jan 1 | Jan 6 | Jan 9 | Jan 13 | Jan 16 | Jan 22 | Jan 29 | Feb 3 |
| First 20° | Dec 14 | Dec 24 | Dec 31 | Jan 4 | Jan 8 | Jan 13 | Jan 16 | Jan 23 | Feb 1 |
| First 24° | Dec 1 | Dec 6 | Dec 16 | Dec 23 | Dec 29 | Jan 1 | Jan 6 | Jan 12 | Jan 20 |
| First 28° | Nov 13 | Nov 21 | Nov 27 | Dec 1 | Dec 4 | Dec 9 | Dec 16 | Dec 25 | Jan 2 |
| First 32° | Nov 2 | Nov 7 | Nov 11 | Nov 15 | Nov 18 | Nov 23 | Nov 27 | Dec 1 | Dec 9 |
| First 36° | Oct 23 | Oct 27 | Nov 1 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 22 |
What's a safe temperature for tender plants? Frost can form on plants even when the air temperature is above 32°. This happens because of radiative cooling. On clear nights, surfaces like leaves and the ground radiate their heat to the cold night sky. As dew forms on these surfaces, those water droplets continue losing heat and can reach freezing even when the surrounding air is a few degrees warmer. This is why frost is more common on clear, calm nights (clouds act as insulation against this heat loss) and why low-lying areas frost first, since the coldest air settles near the ground. So many factors come into play, including wind, cloud cover, nearby structures, trees, and terrain. 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 14. 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 20, so we don't dare plant that early. We wait a few days and by April 1 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 11 | Feb 3 | Jan 31 | Jan 27 | Jan 20 | Jan 15 | Jan 11 | Jan 7 | Jan 1 |
| Last 20° | Mar 2 | Feb 18 | Feb 10 | Feb 3 | Jan 31 | Jan 25 | Jan 18 | Jan 12 | Jan 3 |
| Last 24° | Mar 16 | Mar 8 | Feb 28 | Feb 21 | Feb 15 | Feb 8 | Feb 3 | Jan 28 | Jan 17 |
| Last 28° | Mar 25 | Mar 19 | Mar 16 | Mar 12 | Mar 7 | Mar 1 | Feb 25 | Feb 17 | Feb 6 |
| Last 32° | Apr 3 | Mar 31 | Mar 27 | Mar 24 | Mar 20 | Mar 17 | Mar 14 | Mar 8 | Feb 28 |
| Last 36° | Apr 14 | Apr 9 | Apr 5 | Apr 3 | Apr 1 | Mar 28 | Mar 25 | Mar 20 | Mar 16 |
Now that you know your frost dates, use our Garden Planting Calendar for Batesburg, SC 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.
The Victory Seed Company is family owned and operated, working to help fellow gardeners succeed by selling popular vegetable, herb and flower seeds. Since the 1990s they have been heavily involved with the preservation of rare, open-pollinated, heirloom seeds. Visit them at www.VictorySeeds.com.