In Burlington, Vermont, the last spring frost typically falls between April 30 and May 10, and the first fall frost arrives between October 3 and October 13, according to NOAA’s 1991-2020 Climate Normals. That gives most home gardens in the Champlain Valley a growing window of roughly five months. But Vermont’s mountains and valleys scramble that number fast, and knowing why matters more than memorizing the dates themselves.
The frost dates for Vermont
The numbers above come from a single weather station, USW00014742, sitting near Lake Champlain in Burlington. NOAA’s National Centers for Environmental Information built these dates from three decades of temperature records, calculating the window where the probability of a 32°F freeze runs between 30% and 70% on any given day. That’s why you see a date range rather than one fixed day: frost isn’t a switch that flips on a calendar date, it’s a probability that shifts a little earlier or later every year depending on the specific weather pattern.
A 30-70% band means exactly what it sounds like. On April 30, there’s roughly a 70% chance of a freeze somewhere near that reading. By May 10, the odds have dropped to around 30%. Plant tender seedlings on April 30 in Burlington and you’re gambling against fairly long odds. Wait until after May 10 and the dice favor you, though nothing in nature promises a guarantee.
Why Burlington isn’t the whole state
Here’s the catch that trips up a lot of gardeners working from statewide averages: Burlington sits directly on Lake Champlain, and that lake is the single biggest reason its frost season runs as long as it does. Large bodies of water absorb heat all summer and release it slowly, which delays the first fall freeze and softens the last spring one. Move away from that shoreline effect and the calculus changes fast.
Head up into the Green Mountains, or out toward the Northeast Kingdom in the state’s northeast corner, and the frost-free window shrinks substantially. Elevation alone can knock a growing season down by weeks, and valley towns tucked between ridgelines often trap cold air overnight, producing frost even when nearby hillsides stay clear. Vermont’s hardiness zones tell the same story: the USDA Plant Hardiness Zone Map places the state anywhere from zone 3b to zone 5b, a spread wide enough to separate crops that thrive from crops that never get the chance to mature.
How long the growing season actually is here
Do the math on the Burlington bands and you get a frost-free stretch of somewhere between about 146 and 166 days, depending on which edge of each date range you land on in a given year. That’s close to five and a half months, which is generous by New England standards and explains why the Champlain Valley supports commercial orchards and vineyards that wouldn’t survive in the state’s higher elevations.
That range isn’t a fixed number you can circle on next year’s calendar. It’s built from thirty years of history, and any single season can run shorter or longer than what the normals suggest. A late cold snap in mid-May or an early frost in the third week of September both fall within normal variation, even though they’d chip weeks off the season a gardener was counting on.
What the hardiness zone spread actually tells you
The USDA hardiness zone system is built on exactly one variable: the average annual extreme minimum temperature at a location, measured over the 1991-2020 period. It says nothing about frost timing, humidity, or how long your growing season runs. It’s a winter-survival metric for perennials, shrubs, and trees, telling you whether a plant rated for zone 5 will make it through an average Vermont winter without dying back to the roots.
That’s why Vermont spans zone 3b to zone 5b rather than sitting in one tidy band. The lowest, coldest pockets in the mountains and the Northeast Kingdom land at 3b, where winter lows can drop below minus 35°F in a hard year. The Champlain Valley near Burlington, moderated by the lake, reaches into 5b territory. A shrub rated hardy to zone 5 might sail through winter in Burlington and die a mile up the nearest mountain road. Zone and frost-free season move somewhat together across the state, but they’re measuring different things, and neither substitutes for the other when you’re deciding what to plant.
Turning these dates into a sowing date
Frost dates only become useful once you translate them into an actual planting calendar, and that translation depends on what you’re growing. Seed packets and transplant tags usually list a number of weeks before or after the last frost date, and that’s the number to work backward or forward from once you’ve settled on which frost window applies to your particular spot.
Cold-hardy crops like peas, spinach, and many lettuces tolerate a light frost and can go in the ground a few weeks before the last spring frost date arrives. Tender crops, tomatoes, peppers, squash, and most annual flowers, need soil and air that have both warmed past frost risk, which means waiting until after the late end of the spring window, not the early end, if you want to avoid replanting.
Working from a range instead of a single day
Because Burlington’s last frost falls somewhere between April 30 and May 10, a cautious approach means treating May 10 as your working target for tender transplants, not April 30. Gardeners who push earlier are betting on a warm year, and some years reward that bet. Others don’t, and a June cold snap so far north can still catch a nine-day-old seedling off guard.
The same logic runs in reverse come fall. The first frost window sits between October 3 and October 13, so if you’re counting backward to figure out when to start a fall crop of broccoli or kale, count from October 3, the earlier and more conservative date, rather than assuming you’ll get the full stretch to October 13.
For county-specific guidance that accounts for local elevation and microclimate, the University of Vermont Extension service publishes planting calendars and soil-testing resources tailored to different parts of the state, available at uvm.edu/extension. That’s a better starting point than a statewide average if you’re gardening outside the Champlain Valley.
Why your own garden differs from this figure
Every number in this article comes from one instrument at one location. Your yard is not that location, and even a few hundred yards can shift frost risk meaningfully. Cold air is heavier than warm air, and it flows downhill at night the same way water does, pooling in low spots, hollows, and the base of slopes. A garden at the bottom of a gentle grade can see frost on a night when a garden fifty feet uphill stays clear.
Open, exposed sites lose heat to the night sky faster than sheltered ones. A vegetable bed tucked against a south-facing wall, protected from wind and radiating stored daytime heat after dark, often runs several degrees warmer overnight than an exposed plot in the middle of an open field. Urban and suburban areas generate their own mild warming too, thanks to pavement, buildings, and general human activity holding onto heat, which is part of why in-town gardens sometimes beat their rural neighbors to a longer season.
Soil type and moisture play a role as well. Bare, moist soil absorbs and holds daytime heat better than soil covered in mulch or dense vegetation, radiating that warmth back up overnight and offering a small buffer against frost. Mulched beds, ironically, can sometimes frost sooner because that insulating layer blocks the soil’s heat from reaching the plants above it.
None of this means the NOAA figures are wrong. It means they describe one station’s history, and your specific combination of elevation, slope, water proximity, and ground cover will push your actual frost dates earlier or later than Burlington’s. Tracking your own yard’s frost timing for even two or three seasons, with a simple outdoor thermometer, tells you more about your garden than any regional average ever will.
Common questions
Are these frost dates the same everywhere in Vermont?
No. They come from the Burlington station, which sits on Lake Champlain and enjoys a longer frost-free season than most of the state. Higher elevations, the Green Mountains, and the Northeast Kingdom run colder and shorter, though the exact figures for those areas aren’t published in the data cited here.
What’s the difference between frost dates and hardiness zones?
Frost dates track when freezing temperatures are likely to occur in spring and fall, shaping your planting calendar. Hardiness zones, built by the USDA on average annual extreme minimum winter temperatures, tell you whether a perennial plant can survive winter in your location. They’re related but answer different questions.
Should I plant on the early or late end of the frost date range?
For tender crops like tomatoes and peppers, planting closer to the later end of the spring frost window (May 10 in Burlington’s case) reduces the risk of losing seedlings to a late cold snap. Gardeners willing to accept some risk, or who can cover plants overnight, sometimes push earlier.
Where can I get frost guidance specific to my county?
The University of Vermont Extension service offers localized planting resources that account for regional differences in elevation and climate across the state, available at uvm.edu/extension.