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