Maryland’s last spring frost typically falls between April 3 and April 16, and the first fall frost arrives between October 26 and November 5, based on NOAA climate data. That’s a frost-free window of roughly six and a half to seven months for most of the state, though mountainous Garrett and Allegany counties run weeks behind that timeline, and the Eastern Shore often thaws out earlier. Where your garden lands in that window depends on exactly which corner of Maryland you’re planting in.
The frost dates for Maryland
These numbers come from a single, specific source: NOAA’s National Centers for Environmental Information, using the 1991-2020 Climate Normals and freeze probabilities at 32°F. The range given, April 3 to April 16 for the last spring frost and October 26 to November 5 for the first fall frost, represents the 30% to 70% probability band. At the early end of that window there’s roughly a 30% chance of a freeze occurring after that date; by the late end, that risk climbs to 70%. It’s a probability curve built from decades of observation, not a hard line drawn on the calendar.
The underlying data comes from one reference weather station, not a statewide average, and that matters more in Maryland than in flatter states because the terrain shifts dramatically over short distances. Western Maryland, Garrett and Allegany counties in particular, sits in the Appalachian highlands, where elevation pushes both frost dates later in spring and earlier in fall, sometimes by weeks compared with the rest of the state. The Eastern Shore runs in the opposite direction: the moderating effect of the Chesapeake Bay and the Atlantic keeps that region milder, often letting gardeners there plant earlier in spring and harvest later into fall than the statewide figures suggest. Central Maryland, including the Baltimore-Washington corridor, sits closest to the reference dates above.
What a “frost date” actually measures is the point at which the temperature is expected to hit 32°F, the threshold at which frost typically forms on exposed surfaces and can damage tender plant tissue. Not every plant reacts to that first cold snap the same way. Cold-hardy crops like kale, spinach, and garlic often shrug off an early frost with little damage, while tomatoes, peppers, and basil are usually killed on contact. That difference is exactly why frost dates function as a planning tool rather than a strict rule: gardeners growing tender crops treat the later end of the spring window as their real starting line, while those growing hardy vegetables have more room to gamble on an earlier date.
How long the growing season actually is here
Stretch the two frost windows out and Maryland’s frost-free season runs somewhere between roughly 193 and 216 days, depending on where in each probability band your particular location and year fall. The 216-day figure comes from pairing the earliest plausible last frost (April 3) with the latest plausible first frost (November 5); the 193-day figure comes from pairing the latest last frost (April 16) with the earliest first frost (October 26). Most seasons land somewhere between those bookends, giving the state roughly six and a half to seven months of frost-free growing.
That’s a long season by East Coast standards, long enough to run a spring crop, a summer crop, and a fall crop through the same garden bed if succession plantings are timed carefully.
What the hardiness zone adds (and doesn’t)
Growing season length is only half the picture. The USDA Plant Hardiness Zone Map, updated in 2023 using 1991-2020 climate normals, places Maryland across zones 5b to 8a. That’s a wide range for a state its size, and it reflects the same terrain effect driving the frost date variation: the mountains of Garrett County land in the cooler 5b-6a range, while the areas around the Chesapeake and the lower Eastern Shore push into 7b and 8a. The hardiness map is built on a single variable, the average annual extreme minimum temperature, which measures something different from frost dates. It tells you what perennials and woody plants can survive the coldest night of a typical winter; it says nothing about your last spring frost or how long your growing season runs. Treat it as a companion figure, not a substitute for the frost dates above.
Because the zone range spans so many bands statewide, a single number isn’t useful for a planting decision. The practical move is to look up your own county or nearest weather station rather than assume you sit in the middle of that 5b-8a spread.
Turning these dates into a sowing date
The frost dates above are a starting point, not a finished calendar. The most reliable way to turn them into an actual sowing date is to work backward from the last spring frost window using the timing printed on seed packets, which specify how many weeks before or after that date to start each crop, whether indoors under lights or directly in the ground.
Because the state figure covers a nine-day spread in spring and a ten-day spread in fall, the safer approach for tender crops is to plant toward the later end of the spring window, April 16 rather than April 3, unless you already know your specific location runs warmer than the reference point. The same logic works in reverse for fall: getting tender crops harvested or covered by October 26 protects against the earlier end of the fall frost window, while gardeners confident in a milder microclimate can push closer to November 5.
Hardy crops, spinach, lettuce, peas, and the brassica family, carry that risk differently. These can go in the ground several weeks ahead of the last frost date because a light freeze rarely kills them outright, and many gardeners direct-sow them as soon as the soil can be worked, sometimes as early as March in the milder parts of the state.
The fall frost date works the same way in reverse for a second planting cycle. Crops meant for a fall harvest, like broccoli or kale, need to be seeded in mid-to-late summer so they mature before the first fall frost window closes in. Counting backward from October 26 rather than November 5 builds in a safety margin for gardeners outside the mildest parts of the state.
For a planting calendar built around county-level data rather than a single statewide range, the University of Maryland Extension publishes localized guidance and can serve as a better reference once you know your own hardiness zone and frost pattern. Local extension offices also track soil temperature, which matters more than air temperature for germinating crops like corn, beans, and squash.
Why your own garden differs from this figure
The frost dates published above come from one weather station representing a broad regional pattern, not your backyard. Actual frost timing can shift by days or weeks based on features most gardeners never think to measure.
Elevation and slope matter first. Cold air is heavier than warm air and sinks into low-lying spots, creating frost pockets in valleys and depressions even when nearby higher ground stays frost-free. A garden at the bottom of a slope can see frost weeks earlier in fall and later in spring than a garden a few hundred feet away on higher ground.
Urban and suburban settings add another layer. Pavement, buildings, and concentrated development store heat during the day and release it slowly overnight, an effect known as the urban heat island. Gardens in dense Baltimore neighborhoods or built-up suburbs often see later first frosts and earlier last frosts than open countryside at the same latitude, sometimes shifting the effective frost-free season by a week or more.
Water proximity pulls in the same direction. Gardens near the Chesapeake Bay, the Potomac, or other large bodies of water benefit from water’s slow temperature change, which buffers nearby land from sudden cold snaps in both spring and fall.
Smaller features shift the numbers further: a south-facing wall that radiates stored heat, a dense tree canopy that traps warmer air near the ground, or a raised bed versus ground-level soil. None of that shows up in a climate normal built from decades of station data, which is exactly why the state and county-level figures work best as a baseline to adjust from, not a guarantee to plant by.
Common questions
What is the average last frost date in Maryland?
Based on NOAA’s 1991-2020 Climate Normals, the last spring frost falls between April 3 and April 16 across most of the state. Mountainous western counties run later, and the Eastern Shore tends to run earlier.
Is Maryland in hardiness zone 6 or 7?
Neither answer fits the whole state. The USDA Plant Hardiness Zone Map places Maryland across a range from 5b to 8a, with the coldest zones in Garrett County’s highlands and the warmest near the Chesapeake and lower Eastern Shore. Check your specific county rather than assuming a single statewide zone.
How long is the frost-free growing season in Maryland?
Based on the published frost date ranges, the frost-free season runs roughly 193 to 216 days depending on location and year, which works out to about six and a half to seven months for most of the state.
Where can I find frost dates specific to my county?
The University of Maryland Extension publishes county-level planting guidance that goes beyond the statewide averages cited here, and is the better reference once you know your own hardiness zone and local microclimate.