Frost Dates: First and last frost dates for porterville, 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 April 22. 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 14 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Jan 9 | Dec 27 | Dec 10 | -- | -- | -- | -- | -- | -- |
| Last 28° | Feb 8 | Jan 27 | Jan 18 | Jan 10 | Jan 2 | Dec 25 | Dec 13 | -- | -- |
| Last 32° | Mar 20 | Mar 6 | Feb 24 | Feb 16 | Feb 8 | Jan 31 | Jan 23 | Jan 13 | Dec 30 |
| Last 36° | Apr 22 | Apr 8 | Mar 30 | Mar 21 | Mar 14 | Mar 6 | Feb 26 | Feb 16 | Feb 3 |
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 17.
- There is a 50% chance of being hit by a 32° frost starting around November 28
- You have a 80% chance of seeing 32° by December 9
- 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 21 | Jan 6 | -- | -- | -- | -- | -- | -- | -- |
| First 28° | Nov 23 | Dec 2 | Dec 8 | Dec 14 | Dec 20 | Dec 27 | Jan 6 | -- | -- |
| First 32° | Nov 11 | Nov 17 | Nov 21 | Nov 25 | Nov 28 | Dec 2 | Dec 5 | Dec 9 | Dec 15 |
| First 36° | Nov 3 | Nov 7 | Nov 11 | Nov 14 | Nov 17 | Nov 19 | Nov 22 | Nov 26 | Nov 30 |
Data is provided by the NOAA National Centers for Environmental Information.