When Is Your Last Frost Date in Spring?

Don't dig yet! First find out when it's safe to plant outside again.

You've probably come across the advice to wait until after your last frost date in spring to start planting again. So how do you figure out when that is, exactly? The short answer: You can get a pretty good idea of when it will be based on when the last spring frost date has occurred in past years in your region. You can also plant certain vegetables and flowers outside even before the last frost. Here's what you need to know about your spring frost date so you can avoid any frozen plants.

gloved hands planting tomato seedling in soil

Getty Images / Alina Bitta

First and Last Frost Dates

A "frost" date really means when temperatures fall to 32°F or lower, which is cold enough to damage leaves or kill young, tender plants. In the most basic sense, your "growing season" is essentially the time between when the last freeze happens in spring (your last frost date) and the first time temps get to freezing later in the year (known as the first frost date). Those events don't happen on the exact same days each year, of course. And the last frost date in Chicago is going to be different than the last frost date in Seattle. However, you can get a pretty good idea of the general timeframe based on when they have occurred in the past.

Courtesy of NOAA

To figure out when you'll likely see the last of ice this winter, take a glance at the map above. It's compiled from 30 years of weather data collected by NOAA National Centers for Environmental Information. For example, if you live in Southern Illinois, you'll probably be able to plant outside during the first part of April, but if you're farther north in Illinois, you should wait till the second half of the month to be safe. You can also get the map information personalized for your zip code through the National Gardening Association's online database.

By using these guidelines, you'll have a window for planting outside. However, spring weather can often shift quickly, so make your local weather forecasters your BFFs. They'll warn you about any sudden temperature drops coming your way. If that happens, make sure to bring in any tender plants in containers or cover newly planted veggies or annuals with an old cotton sheet until the weather warms again.

What to Plant Outside Before the Last Frost Date

Your heat-loving tomato seedlings will definitely have to wait for warmer weather, but you can go ahead and start growing cool-season vegetables and flowers. These unsung heroes of the garden are cold-hardy crops that you can grow as the temperatures are still chilly (and even a little frosty) in spring. You can even replant them again in late summer for fall color and harvests.

As long as your soil has thawed out enough to dig in, you can sow most cool-season vegetables right in the garden rather than starting them indoors first. These include leafy greens like Swiss chard, kale, and spinach. Radishes also grow quickly in spring and tolerate frost well.

Certain annual flowers like pansies and snapdragons that often appear at garden centers very early in the spring also can take mild freezing temperatures and keep on blooming. Bare-root trees (especially fruit trees hardy in your area) can also be planted before your last frost date—because they haven't started to actively grow new leaves yet, they won't be harmed by a little below-freezing weather.

So, don't let a couple of warm days in early spring fool you into setting out your homegrown seedlings or new plant babies from the garden center too soon. Prevent a cold snap from withering your garden by knowing your area's last spring frost date and keeping an eye on the weather.

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