Frost dates for Williston Exp. Farm, ND
At Williston Exp. Farm, the median last spring frost (32°F) is May 13 and the median first fall frost is Sep 26, for a typical growing season of 135 days. For a 90% chance that the last frost has passed, wait until May 25. Nearby ZIP codes are in USDA hardiness zone 4a.
- May 13Last spring frost (median)50% chance of 32°F after this date
- May 25Safer planting date10% chance of 32°F after this date
- Sep 26First fall frost (median)50% chance of 32°F by this date
- 135 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 12 | May 23 | Jun 6 |
| 32°F | May 1 | May 13 | May 25 |
| 28°F | Apr 18 | May 3 | May 17 |
| 24°F | Apr 7 | Apr 23 | May 5 |
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 6 | Sep 19 | Sep 30 |
| 32°F | Sep 14 | Sep 26 | Oct 8 |
| 28°F | Sep 21 | Oct 3 | Oct 18 |
| 24°F | Sep 29 | 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 | 99 days | 117 days | 133 days |
| 32°F | 117 days | 135 days | 153 days |
| 28°F | 134 days | 154 days | 174 days |
| 24°F | 153 days | 175 days | 194 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 |
|---|---|---|---|
| 58853 | 4a | -30 to -25°F | 9 km |
| 58801 | 4a | -30 to -25°F | 11 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 USC00329430, at 48.1375, -103.7372, elevation 642 m (2,105 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 176.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Williston Sloulin Intl Airport (8 km)
- Watford City (50 km)
- Keene 3s (66 km)
- Tioga 1e (67 km)
- Watford City 14s (70 km)
- Wildrose 3nw (70 km)
- Fortuna 1 W (86 km)
- Grassy Butte 2ene (91 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.