Generally, you hear about the 'average last frost date'. But I don't really like planning my planting dates based on that because it is the AVERAGE last date--meaning half of the time the last frost is before that date, and half of the time it is after.
|"You mean to tell me that there is a 50% chance that I'll |
endure freezing weather when you plant me out on the
average last frost date??" -Tomatoes
It includes 3 different temperatures (28, 32 and 36) and 3 different probability levels (10, 50 and 90). Below is the pertinent information for Chapel Hill, NC:
|Better than your average last frost data for Chapel Hill, North Carolina.|
On the flip side, April 30 is the 10% probability level for 32 degrees. This means that 1 time out of 10, a temperature as cold or colder than 32 will occur later than April 30. I'm willing to accept a 10% frost risk when planting out tomatoes. For more sensitive plants (like eggplants and squash) I would probably wait another week or two.
For the fall season, the probability level represents the chance of NOT having a temperature as cold or colder earlier than the computed date.
Given the above odds for various temperatures (and the projected forecast), I think I'll plant out my tomatoes sometime later this week!