In the Twin Cities area, the station that anchors Minnesota’s official climate data, the last spring frost typically falls between April 17 and April 30, and the first fall frost lands between October 11 and October 23. That’s the mild southern edge of the state. Northern Minnesota tightens both ends by two to three weeks, so treat these numbers as a starting point, not a statewide guarantee.
The frost dates for Minnesota
Those two windows, April 17 to April 30 in spring and October 11 to October 23 in fall, come from NOAA’s National Centers for Environmental Information, using the 1991-2020 Climate Normals for station USW00014922. That station sits in the Twin Cities metro, which means every date on this page describes south-central Minnesota’s climate, not the Iron Range or the Arrowhead.
The dates aren’t single-day predictions. They mark what NOAA calls the 30-70% freeze probability band: the stretch of the calendar where the odds of a 32°F freeze shift from likely to unlikely. On April 17, there’s roughly a 70% chance of still hitting freezing at some point. By April 30, that risk has dropped to around 30%. Pick a date inside that window and you’re choosing how much risk you’re willing to carry, not reading a fixed cutoff.
This matters because a lot of garden advice treats “last frost date” as one number, like a light switch. It isn’t. A frost on April 22 falls squarely inside the normal range for this station, not as an outlier. Gardeners who plant tender starts on April 18 and lose them to a cold night on April 25 haven’t been unlucky in any unusual sense. They’ve landed on the wrong side of a probability that was always sitting near 50/50.
The same logic applies in fall. October 11 marks the point where freeze odds start climbing past 30%; October 23 is where they cross 70%. A frost on October 15 is common, not rare, for the Twin Cities. Gardeners farther north should expect that whole band to shift earlier, sometimes by two weeks, sometimes by three, depending on elevation and distance from Lake Superior’s moderating effect.
Here’s the practical takeaway: if you garden in the Twin Cities or a similarly situated southern Minnesota location, these two windows are usable as written. If you garden near Duluth, International Falls, or anywhere along the northern tier, shift both dates earlier in spring’s end and fall’s start, and lean on University of Minnesota Extension for county-level detail this page can’t provide.
How long the growing season actually is here
Stack the two windows together and Minnesota’s frost-free season runs somewhere between 164 and 189 days, depending on where inside each band your actual frost lands. The shorter estimate pairs the latest spring frost (April 30) with the earliest fall frost (October 11); the longer one pairs the earliest spring frost (April 17) with the latest fall frost (October 23). Most years fall somewhere between those two figures, not neatly at either edge.
That’s roughly five and a half to six and a quarter months of frost-free growing, at least for the reference station. Compare that to a state like Georgia, where frost-free stretches run eight months or more, and Minnesota’s compressed timeline starts to explain why the state’s seed-starting culture leans so heavily on indoor starts and season-extension tools like row cover and cold frames.
USDA’s Plant Hardiness Zone Map, built from the same 1991-2020 climate period, places Minnesota across zones 3a to 5a. That system measures something different from frost dates, though: it’s built entirely on the average annual extreme minimum winter temperature, not on spring or fall freeze timing. A location can share a frost-free season length with another town and still sit in a different hardiness zone if its coldest winter nights run harder. The Twin Cities lean toward the warmer end of that Minnesota range; far northern counties sit closer to zone 3a, where winter lows drop lower and, generally, the growing season compresses further.
What this means for planning: don’t lean on hardiness zone alone to guess your frost-free window. Zone tells you what perennial shrub or fruit tree might survive winter. It doesn’t tell you when to safely move tomato seedlings outside. Those are two separate questions, answered by two separate datasets, and conflating them is one of the more common mistakes gardeners make when reading seed packets that reference “zone” language loosely.
Turning these dates into a sowing date
Seed packets and transplant schedules almost always reference “last frost date” as the anchor point, counting backward for indoor starts and forward for outdoor moves. With a window instead of a single date, the safer approach is to build in a buffer rather than gamble on the early edge.
For cold-tolerant crops, hardy transplants like broccoli, cabbage, and kale generally go into the ground two to four weeks before the last frost, since a light freeze doesn’t damage them the way it damages tender seedlings. Peas and spinach, direct-sown rather than started indoors, typically go into workable soil around that same early window, sometimes even earlier if the ground has thawed and drained.
Warm-season crops work the opposite way. Tomatoes, peppers, squash, and cucumbers are frost-sensitive at the seedling stage and generally wait until after the last frost date has safely passed, often with growers adding another week or two beyond that for soil to warm enough for good root growth. Using April 30, the later end of the Twin Cities window, as your working assumption rather than April 17 costs you two weeks of season but sharply cuts the odds of losing a tray of seedlings to a cold snap.
On the fall side, the math runs backward. Look up the “days to maturity” listed on a seed packet, then count back from your chosen fall frost date, October 11 if you want the cautious estimate, October 23 if you’re comfortable with more risk, to find the latest safe planting date for that crop to mature before cold shuts things down.
For anyone gardening outside the Twin Cities metro, none of this replaces a local check. University of Minnesota Extension maintains county-specific guidance and planting calendars built around regional climate data, which matters more the farther you are from the reference station this page is built on.
Why your own garden differs from this figure
The NOAA station generating these dates sits at a specific airport location: open, elevated slightly, exposed to wind. That’s a deliberate choice for consistent long-term measurement, but it also means the number rarely matches a backyard.
Low spots collect cold air on calm nights, since cold air is denser and drains downhill the same way water does. A garden bed at the bottom of a slope can run several degrees colder overnight than one just fifty feet away on higher ground. A brick wall or paved driveway holds daytime heat and releases it slowly after dark, which is why plants tucked against a south-facing foundation often dodge frosts that hit the open lawn nearby.
Cities complicate this further. Pavement, buildings, and concentrated heat sources push urban temperatures higher than surrounding rural land, an effect strong enough that some Twin Cities neighborhoods likely see later spring frosts and earlier fall frosts than open countryside just a few miles out, even though both sit under the same official station’s data.
Elevation plays a role too, particularly as you move toward Minnesota’s northern reaches, where terrain varies more and the moderating influence of Lake Superior only reaches communities close to the shoreline. A garden ten miles inland from the lake can run noticeably colder than one right along the water.
None of this means the NOAA figures are wrong. It means they describe one specific location’s climate record, and every other yard sits somewhere on a spectrum around that number. Tracking your own site’s First and Last Frost over a few seasons, with a simple outdoor thermometer log, tells you more about your specific garden than any regional average ever will.
Common questions
Is all of Minnesota in the same USDA hardiness zone?
No. The state spans zones 3a through 5a on the USDA Plant Hardiness Zone Map, with northern counties running colder and the Twin Cities area sitting toward the warmer end of that range.
Do these frost dates apply to northern Minnesota?
Not directly. The published dates come from a Twin Cities-area station. Northern Minnesota’s frost season generally runs two to three weeks tighter on both ends, with spring’s last frost later and fall’s first frost earlier, though specific figures for those areas aren’t published in this dataset.
Can frost still happen after the “last frost date”?
Yes. The date marks a 30% freeze probability, not zero. A frost after April 30 in the Twin Cities isn’t rare, it’s simply less likely than it was two weeks earlier.
Where can I find frost data specific to my county?
University of Minnesota Extension publishes county-level growing guides and planting calendars that account for local variation this statewide figure can’t capture.