Frost dates for Helena 1 SSE, OK
At Helena 1 SSE, the median last spring frost (32°F) is Apr 9 and the median first fall frost is Oct 31, for a typical growing season of 205 days. For a 90% chance that the last frost has passed, wait until Apr 23. Nearby ZIP codes are in USDA hardiness zone 7a.
- Apr 9Last spring frost (median)50% chance of 32°F after this date
- Apr 23Safer planting date10% chance of 32°F after this date
- Oct 31First fall frost (median)50% chance of 32°F by this date
- 205 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 | Apr 4 | Apr 19 | May 2 |
| 32°F | Mar 25 | Apr 9 | Apr 23 |
| 28°F | Mar 9 | Mar 31 | Apr 14 |
| 24°F | Feb 27 | Mar 15 | Apr 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 | Oct 11 | Oct 23 | Nov 4 |
| 32°F | Oct 18 | Oct 31 | Nov 13 |
| 28°F | Oct 25 | Nov 8 | Nov 23 |
| 24°F | Nov 1 | Nov 18 | Dec 3 |
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 | 166 days | 186 days | 206 days |
| 32°F | 184 days | 205 days | 227 days |
| 28°F | 203 days | 225 days | 250 days |
| 24°F | 221 days | 247 days | 271 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 |
|---|---|---|---|
| 73741 | 7a | 0 to 5°F | 2 km |
| 73739 | 7a | 0 to 5°F | 12 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 USC00344019, at 36.5381, -98.2661, elevation 412 m (1,350 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 105.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Lahoma 1wsw Mesonet (22 km)
- Cherokee 1ssw Mesonet (25 km)
- Great Salt Plains Dam (26 km)
- Cherokee 4w (29 km)
- Fairview 1w Mesonet (37 km)
- Enid (37 km)
- Alva 7ssw Mesonet (44 km)
- Okeene (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.