Mandan, ND planting zone & frost dates
Mandan is in USDA hardiness zone 4a. The last spring frost usually comes around May 13 and the first fall frost around September 27, for a growing season of about 136 days.
Planting calendar for Mandan
Dates are counted from the average last spring frost (May 13) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 18 – Apr 1 Transplant outdoors: May 20 – May 27 |
| Peppers | Start seeds indoors: Mar 4 – Mar 18 Transplant outdoors: May 27 – Jun 3 |
| Eggplant | Start seeds indoors: Mar 4 – Mar 18 Transplant outdoors: May 27 – Jun 3 |
| Broccoli | Start seeds indoors: Mar 4 – Mar 18 Transplant outdoors: Apr 15 – Apr 29 |
| Cabbage | Start seeds indoors: Mar 4 – Mar 18 Transplant outdoors: Apr 15 – Apr 29 |
| Onions (sets) | Plant outdoors: Apr 15 – Apr 29 |
| Peas | Sow outdoors: Apr 1 – Apr 15 |
| Spinach | Sow outdoors: Apr 1 – Apr 15 |
| Lettuce | Sow outdoors: Apr 15 – Apr 29 |
| Carrots | Sow outdoors: Apr 15 – Apr 29 |
| Potatoes | Plant outdoors: Apr 15 – Apr 29 |
| Beans | Sow outdoors: May 20 – May 27 |
| Sweet corn | Sow outdoors: May 20 – May 27 |
| Cucumbers | Sow outdoors: May 20 – May 27 |
| Squash & zucchini | Sow outdoors: May 20 – May 27 |
| Basil | Start seeds indoors: Apr 1 – Apr 15 Transplant outdoors: May 20 – May 27 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 2 (8 weeks before the average first fall frost on Sep 27).
Useful for zone 4a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | May 1 | May 13 | May 26 |
| First 32°F frost in fall is before | Oct 10 | Sep 27 | Sep 15 |
How to read it: in spring there is a 10% chance of a frost after May 26, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 15. A hard freeze (28°F) usually ends around May 3.
Hardiness zone by ZIP code in Mandan
- 58554 zone 4a
Nearby cities
- Bismarck zone 4a, last frost May 10
- Minot zone 4a, last frost May 10
- Dickinson zone 4a, last frost May 20
- Jamestown zone 4b, last frost May 8
- Williston zone 4a, last frost May 21
- West Fargo zone 4a, last frost May 10
- Grand Forks zone 4a, last frost May 10
- Fargo zone 4a, last frost May 5
Questions
What growing zone is Mandan, ND?
Mandan is in USDA Plant Hardiness Zone 4a (average extreme winter low -30°F to -25°F), according to the USDA 2023 map.
When is the last frost in Mandan?
The average last spring frost (32°F) in Mandan is May 13. There is still a 10% chance of frost until May 26.
When can I plant tomatoes in Mandan?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 20 – May 27. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Mandan Exp Stn, ND (USC00325479), 2.2 km (1.4 mi) from the city center, elevation 533 m, based on 30 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.