Your Last Spring Frost Date Tells You When it's Safe to Plant Outside Again Don't let a couple of warm days in early spring fool you into setting out your seedlings or new plants You'll need to wait until after your last frost date to add any new plants to your yard. But when is that, exactly? Here's what you need to know about your last frost-free date, so you can avoid frozen plants. The "growing season" is the time between the last freeze in spring and the first freeze later in the year. That doesn't happen on the same days each year, but you can get a good idea of the time frame based on the average dates in the past. To figure out when you'll likely see the last of ice this winter, take a glance at this map. It's compiled from 30 years of weather data collected by NOAA. And while you’re impatiently waiting to get your tomato seedlings in the ground, it's a great time to start growing cool-season vegetables and flowers. As long as your soil has thawed out enough to dig in, you can sow cool-season vegetables in the garden rather than starting them indoors first.