First and Last Frost Dates, Explained

Why frost dates are the backbone of every planting schedule, how to find yours, and how to plant around them.

If you only learn two dates as a gardener, learn these: your average last spring frost and your average first fall frost. Together they define your growing season, and nearly every planting date is measured from one of them.

The last spring frost

This is the average date after which a hard freeze becomes unlikely. Tender, warm-season crops like tomatoes, peppers, and basil wait until after it to go outside. Cool-season crops like peas and spinach can go out weeks before it, because a light frost does not bother them.

The first fall frost

This is the average date when freezing nights return in autumn. It is the deadline for your warm-season harvest, and the anchor for crops you plant in late summer to overwinter, like garlic. Counting backward from this date tells you the last day it is worth sowing a fall crop.

How to use them

Find your frost dates by zone on any zone page. Remember they are averages, not guarantees. A late spring frost can still arrive after the average date, so keep an eye on the forecast and cover tender plants on a cold night. Dibble can send a frost alert before a cold night so you are not caught out.

Common questions

What is the last frost date?

It is the average date of the last spring frost in your area. After it, the risk of a freeze drops enough to plant tender crops outside. It is an average, so a late frost is always possible.

Why do frost dates matter so much?

Almost every planting time is measured against them. Tender crops wait until after the last spring frost; many cool-season and overwintering crops are timed to the first fall frost.

How accurate are they?

They are long-term averages. Treat them as a strong guide, watch your local forecast near the date, and protect tender plants if a cold night is coming.