Frost dates for Bismarck 2.4 NNW, ND
At Bismarck 2.4 NNW, the median last spring frost (32°F) is May 10 and the median first fall frost is Sep 30, for a typical growing season of 142 days. For a 90% chance that the last frost has passed, wait until May 23. Nearby ZIP codes are in USDA hardiness zone 4a.
- May 10Last spring frost (median)50% chance of 32°F after this date
- May 23Safer planting date10% chance of 32°F after this date
- Sep 30First fall frost (median)50% chance of 32°F by this date
- 142 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 8 | May 20 | Jun 2 |
| 32°F | Apr 30 | May 10 | May 23 |
| 28°F | Apr 18 | May 1 | May 13 |
| 24°F | Apr 8 | Apr 21 | May 4 |
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 8 | Sep 21 | Oct 4 |
| 32°F | Sep 16 | Sep 30 | Oct 13 |
| 28°F | Sep 25 | Oct 9 | Oct 22 |
| 24°F | Oct 2 | Oct 18 | Nov 1 |
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 | 105 days | 123 days | 142 days |
| 32°F | 124 days | 142 days | 159 days |
| 28°F | 140 days | 161 days | 179 days |
| 24°F | 158 days | 177 days | 197 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 58505 | 4a | -30 to -25°F | 2 km |
| 58503 | 4a | -30 to -25°F | 9 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 USC00320817, at 46.8339, -100.7969, elevation 558 m (1,831 ft).
- Data quality: Representative (10+ years), 12 years of freeze data.
- Average days per year at or below 32°F: 181.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Bismarck WFO (7 km)
- Bismarck (8 km)
- Mandan Exp. Station (9 km)
- Wilton (36 km)
- Center 4se (41 km)
- Moffit 3 SE (47 km)
- Hazelton 4nw (49 km)
- Breien (52 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.