When to plant in Mandan, ND
USDA Zone 4aEverything below — frost dates, hardiness zone, and what to plant when in Mandan, North Dakota — is derived from the closest NOAA station with complete climate normals.
Zone 4a is cold — in Mandan, most perennials must be fully hardy, and your frost dates set a tight window for tender annual vegetables.
Frost probability
MANDAN EXP STN · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Mandan’s own odds, recorded at MANDAN EXP STN.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 4 | May 23 | May 10 | Sep 6 | Sep 19 | Oct 1 |
| 32°F | May 26 | May 13 | May 1 | Sep 15 | Sep 27 | Oct 10 |
| 28°F | May 17 | May 3 | Apr 19 | Sep 23 | Oct 4 | Oct 19 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Mandan, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 12 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Mandan planting FAQ
When is the last spring frost in Mandan, ND?
Mandan's average last spring frost falls near May 13 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Mandan, ND?
Expect Mandan's first fall frost near September 27 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Mandan in?
Mandan is in USDA hardiness zone 4a. In zone 4a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Mandan?
There are roughly 137 frost-free days in Mandan (a short growing season), running from the average last frost around May 13 to the first fall frost near September 27.
When should I plant tomatoes in Mandan?
In Mandan, start tomato seeds indoors around March 18–April 1, then transplant seedlings outdoors around May 20 once the danger of frost has passed.
Never miss a window in Mandan
An email when it’s time to start seeds, transplant, and sow — timed to Mandan’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at MANDAN EXP STN, 3 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Mandan, ND — Frost Dates & Zone 4a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00325479. Retrieved from https://blissgarden.com/north-dakota/mandan.