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