Frost dates for Bismarck, ND
At Bismarck, the median last spring frost (32°F) is May 14 and the median first fall frost is Sep 27, for a typical growing season of 136 days. For a 90% chance that the last frost has passed, wait until May 27. Nearby ZIP codes are in USDA hardiness zone 4a.
- May 14Last spring frost (median)50% chance of 32°F after this date
- May 27Safer planting date10% chance of 32°F after this date
- Sep 27First fall frost (median)50% chance of 32°F by this date
- 136 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | May 11 | May 25 | Jun 7 |
| 32°F | May 1 | May 14 | May 27 |
| 28°F | Apr 20 | May 3 | May 17 |
| 24°F | Apr 10 | Apr 25 | May 8 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Sep 7 | Sep 19 | Sep 29 |
| 32°F | Sep 15 | Sep 27 | Oct 9 |
| 28°F | Sep 22 | Oct 5 | Oct 18 |
| 24°F | Oct 1 | Oct 14 | Oct 27 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 96 days | 116 days | 133 days |
| 32°F | 117 days | 136 days | 153 days |
| 28°F | 135 days | 154 days | 174 days |
| 24°F | 153 days | 173 days | 192 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 58505 | 4a | -30 to -25°F | 6 km |
| 58501 | 4a | -30 to -25°F | 7 km |
| 58504 | 4a | -30 to -25°F | 7 km |
| 58554 | 4a | -30 to -25°F | 14 km |
| 58503 | 4a | -30 to -25°F | 15 km |
| 58558 | 4a | -30 to -25°F | 19 km |
| 58566 | 4a | -30 to -25°F | 24 km |
| 58521 | 4a | -30 to -25°F | 29 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USW00024011, at 46.7708, -100.7603, elevation 505 m (1,658 ft).
- Data quality: Standard (24+ years of data), 26 years of freeze data.
- Average days per year at or below 32°F: 184.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Bismarck WFO (0 km)
- Bismarck 2.4 NNW (8 km)
- Mandan Exp. Station (12 km)
- Moffit 3 SE (42 km)
- Hazelton 4nw (42 km)
- Wilton (43 km)
- Breien (46 km)
- Center 4se (47 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.