Frost Dates: First and last frost dates for fairfield rs, id
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 26. 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 17, so we don't dare plant that early. We wait a few days and by March 16 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 13 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Jan 18 | Jan 3 | Dec 18 | -- | -- | -- | -- | -- | -- |
| Last 28° | Feb 2 | Jan 24 | Jan 18 | Jan 11 | Jan 4 | Dec 25 | -- | -- | -- |
| Last 32° | Mar 16 | Mar 3 | Feb 22 | Feb 14 | Feb 7 | Jan 30 | Jan 22 | Jan 11 | Dec 21 |
| Last 36° | Apr 26 | Apr 12 | Apr 2 | Mar 24 | Mar 16 | Mar 8 | Feb 27 | Feb 17 | 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 21.
- There is a 50% chance of being hit by a 32° frost starting around December 6
- You have a 80% chance of seeing 32° by December 23
- 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 25 | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 10 | Dec 28 | Jan 16 | -- | -- | -- | -- | -- | -- |
| First 28° | Nov 28 | Dec 9 | Dec 17 | Dec 25 | Jan 3 | Jan 19 | -- | -- | -- |
| First 32° | Nov 14 | Nov 21 | Nov 27 | Dec 2 | Dec 6 | Dec 11 | Dec 16 | Dec 23 | Jan 4 |
| First 36° | Nov 1 | Nov 8 | Nov 12 | Nov 16 | Nov 20 | Nov 24 | Nov 28 | Dec 2 | Dec 9 |
Data is provided by the NOAA National Centers for Environmental Information.