Frost Dates: First and last frost dates for Charleston Intl., SC
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 March 28. 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 February 16, so we don't dare plant that early. We wait a few days and by March 4 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.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | Jan 21 | Jan 9 | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Feb 13 | Feb 2 | Jan 24 | Jan 15 | Dec 30 | -- | -- | -- | -- |
| Last 28° | Feb 23 | Feb 13 | Feb 6 | Jan 30 | Jan 24 | Jan 17 | Jan 9 | Dec 28 | -- |
| Last 32° | Mar 8 | Feb 27 | Feb 20 | Feb 14 | Feb 9 | Feb 4 | Jan 29 | Jan 22 | Jan 13 |
| Last 36° | Mar 28 | Mar 20 | Mar 14 | Mar 9 | Mar 4 | Feb 27 | Feb 22 | Feb 16 | Feb 8 |
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
- You have a small 20% chance of getting 32° by December 6.
- There is a 50% chance of being hit by a 32° frost starting around December 22
- You have a 80% chance of seeing 32° by January 6
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 20° | Jan 8 | Jan 21 | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 27 | Jan 7 | Jan 17 | Jan 27 | Feb 14 | -- | -- | -- | -- |
| First 28° | Dec 12 | Dec 20 | Dec 27 | Jan 1 | Jan 6 | Jan 12 | Jan 19 | Jan 29 | -- |
| First 32° | Nov 28 | Dec 6 | Dec 12 | Dec 17 | Dec 22 | Dec 27 | Jan 1 | Jan 6 | Jan 15 |
| First 36° | Nov 12 | Nov 19 | Nov 25 | Nov 30 | Dec 5 | Dec 9 | Dec 14 | Dec 20 | Dec 28 |
Data is provided by the NOAA National Centers for Environmental Information.