Do You Know Your First Frost and Last Frost Dates?

First and last frost dates are referred to frequently in gardening. Do you know yours?

You see it on the back of every seed packet: plant after last frost date, or start seeds 8 weeks before the last frost date.

But how do you know exactly when your first or last frost date is, especially when you’re new to gardening? If you plant too early in spring, you risk killing your seedlings with frost. Plant too late in spring, and you might end up with a very late harvest, if at all. If you get surprised by an early frost in fall, your green tomatoes are lost. Timing is everything.

Unfortunately, there is a lot of junk information on the web about first and last frost dates. The problem is, these dates don’t fall on specific days, but within a window of about 6 weeks, and there’s also significant variation within hardiness zones. Where it falls in your area year to year depends upon how warm or cold your season is, and Mother Nature’s whims.

When is the first frost date and last frost date?

• The most reliable source of first and last frost and freeze dates is the National Centers For Environmental Information (formerly the National Climatic Data Center), a division of NOAA, the zen masters of weather forecasting. Their information is based on historical weather data collected since 1971, organized by state and local regions. Find the National Weather Service info on your first fall freeze and last spring freeze here.
• Daves Garden has an easy-to-use first and last freeze dates table here, which you can look up by zip code and is probably sufficient for most gardeners.

Knowing where your first frost date and last frost date fall is essential to gardening success. Every gardener eventually becomes somewhat of a weather junkie – if you’re not in tune with the weather in your area, even in mid-season, you run the risk of damage or a premature end to your fruits, veggies, and tender plants. Frost, drought, heatwaves, wind, heavy rain, or whatever else nature cooks up for you are all manageable. Forewarned is forearmed.

Why knowing your first frost date and last frost date matters

First frost

Most of the vegetables we plant are annuals and can’t survive heavy frosts. The same is true for many of the most beautiful flowers we grow, like Dahlias, Cala Lilies, Caladium, and others. When I see my first frost warning in the fall, I rush to the garden to harvest as many tomatoes and peppers as possible, as they won’t survive more than a light touch of frost. If the frost is heavy, or if the tomatoes and peppers are exposed to a freeze, they’re inedible. Greens like Kale actually enjoy a little frost and become a little sweeter. Before a freeze occurs, sensitive flower bulbs must be lifted and stored indoors. Many will not survive winter. Check your hardiness for more information on what will and won’t survive in your area.

Last frost

The last frost in spring is an important marker, too. This is typically the mark at which it’s safe to plant tomatoes, peppers, and annual flowers (although soil temperature factors in too). Many greens can be planted about 4 weeks before the last frost. There are a few tricks one can use to plant before your last frost like milk jugs to cover the tender plants.

Freeze & Frost Date resources:

• National first freeze dates (fall)
• National Gardening Association (national by zip code)
• NOAA When to expect your last spring frost