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Updated: April 10, 2024

Can you tell me the date of the last frost in my area?

To find your average last frost date, these are two resources we recommend:

  1. Purdue University's Freeze Date Tool. Select your county on the map to get your last average freeze date.
  2. The National Gardening Association's Frost Dates by Zip Code.

From The National Gardening Association page, you will receive a chart like in the example below:

Frederick, MD 10% 30% 50% 70% 90%
Last 32° Apr 19 Apr 13 Apr 9 Apr 4 Mar 29

The chart indicates a 10% chance that the temperature will go down to 32°F on April 19. There is a 90% chance of 32°F on March 29. In other words, April 19 has a lower probability of a freeze and would be a "safer" planting date. You would still have to monitor your local weather forecast. This data is derived from the 1991–2020 U.S. Climate Normals from NOAA.

Why is the last frost date so important to gardeners?

Much planning and effort go into planting a vegetable and flower garden and so gardeners anticipate this date with great expectation. The last frost date in the spring and the first frost date in the fall dictate how long your growing season will be. If you want to grow plants from seeds indoors, you need this date in order to determine when to start your seeds. If you buy plants from a garden center or nursery, it is important to know this date so you can plan when to put your plants in the garden and minimize the risk of cold damage.

Three important things to keep in mind:

  1. The likelihood of frost will vary between landscapes in the same town or even neighborhood, due to many factors such as changes in wind, elevation, proximity to buildings, and water.
  2. Avoid the temptation to put tender annual plants in the ground too early. You might be eager to plant warm-season tomatoes, basil, peppers, and annual flowers that are set out early at the garden centers, but you take a gamble if you put them in the ground when it is too cold. Tender plant roots may not be able to absorb nutrients from cold wet soils, which will lead to poor growth later on. In most areas of Maryland, it is generally safe to plant tender annuals by the second week of May.
  3. Early in the season, after planting outdoors, closely monitor weather reports for news of an unexpected frost. If predicted, be prepared to protect your tender plants. Many a new gardener has been surprised by an unexpected frost! Learn how to protect your plants with a  row cover.

Still have a question? Contact us at Ask Extension.