Spring Frost/Freeze Dates in Maryland

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

We know spring is in the air when this question begins to be asked by Maryland residents who contact our horticulturists. While this date can fluctuate from year to year, historical temperature data provides a guide to help predict this very important date.

To find your average last frost date, enter your location or zip code into the frost date app from The National Gardening Association: https://garden.org/apps/frost-dates/.

You will receive a chart like the example below:

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 1981–2010 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. (See Frost and Cold Injury.) 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 floating row cover.