How to read these charts for the spring
As the growing season approaches, the days get longer, the weather begins to warm up, and the nights start being less cold. You’re still getting frost, but the chance of nightly frosts gets less and less with each passing day. Eventually, the frost stops, and this is when your tender plants are fully safe. So, how do you plan for this? The probabilities on this page help you assess your risk of frost on any given day.
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 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 April 21, so we don’t dare plant that early. We wait a few days and by May 2 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.
In The Spring
| Tmp | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | Mar 23 | Mar 15 | Mar 10 | Mar 5 | Feb 28 | Feb 24 | Feb 19 | Feb 14 | Feb 6 |
| Last 20° | Apr 4 | Mar 28 | Mar 23 | Mar 19 | Mar 15 | Mar 12 | Mar 8 | Mar 3 | Feb 24 |
| Last 24° | Apr 13 | Apr 7 | Apr 2 | Mar 30 | Mar 26 | Mar 23 | Mar 19 | Mar 15 | Mar 9 |
| Last 28° | Apr 22 | Apr 17 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Apr 1 | Mar 28 | Mar 23 |
| Last 32° | Apr 30 | Apr 25 | Apr 21 | Apr 17 | Apr 14 | Apr 11 | Apr 8 | Apr 4 | Mar 29 |
| Last 36° | May 18 | May 12 | May 8 | May 5 | May 2 | Apr 29 | Apr 25 | Apr 21 | Apr 16 |
How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Owensville, Missouri start to go down, and therefore every day that goes by increases the chance that you’ll get frost. Your risk of frost really begins around September 26, and by October 19 you’re almost certain to have received at least one frost event.
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 October 1.
- There is a 50% chance of being hit by a 32° frost starting around October 10
- You have a 80% chance of seeing 32° by October 19
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
In The Fall
| Tmp | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | Nov 7 | Nov 13 | Nov 18 | Nov 22 | Nov 26 | Nov 29 | Dec 3 | Dec 8 | Dec 15 |
| First 20° | Oct 25 | Nov 2 | Nov 8 | Nov 12 | Nov 17 | Nov 21 | Nov 26 | Dec 2 | Dec 9 |
| First 24° | Oct 18 | Oct 25 | Oct 30 | Nov 3 | Nov 8 | Nov 12 | Nov 16 | Nov 21 | Nov 28 |
| First 28° | Oct 2 | Oct 9 | Oct 13 | Oct 18 | Oct 21 | Oct 25 | Oct 29 | Nov 3 | Nov 10 |
| First 32° | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 24 |
| First 36° | Sep 18 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 6 | Oct 10 | Oct 13 | Oct 18 |
Reference: garden.org