Frost Dates: First and last frost dates for five points, ca
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 6. 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 13, so we don't dare plant that early. We wait a few days and by April 3 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° | Dec 23 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Feb 21 | Jan 28 | Jan 5 | Dec 1 | -- | -- | -- | -- | -- |
| Last 28° | Mar 11 | Feb 22 | Feb 10 | Jan 31 | Jan 21 | Jan 11 | Dec 31 | Dec 16 | Nov 19 |
| Last 32° | Apr 17 | Apr 2 | Mar 23 | Mar 14 | Mar 6 | Feb 26 | Feb 17 | Feb 6 | Jan 23 |
| Last 36° | May 6 | Apr 25 | Apr 17 | Apr 10 | Apr 3 | Mar 28 | Mar 21 | Mar 13 | Mar 1 |
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 November 11.
- There is a 50% chance of being hit by a 32° frost starting around November 22
- You have a 80% chance of seeing 32° by December 3
- 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° | Dec 17 | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 6 | Dec 20 | Jan 4 | -- | -- | -- | -- | -- | -- |
| First 28° | Nov 12 | Nov 22 | Nov 29 | Dec 6 | Dec 12 | Dec 18 | Dec 25 | Jan 2 | Jan 18 |
| First 32° | Nov 6 | Nov 11 | Nov 15 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 3 | Dec 9 |
| First 36° | Oct 22 | Oct 28 | Nov 2 | Nov 6 | Nov 9 | Nov 13 | Nov 16 | Nov 21 | Nov 27 |
Data is provided by the NOAA National Centers for Environmental Information.