Frost dates for Jefferson, IA
At Jefferson, the median last spring frost (32°F) is Apr 26 and the median first fall frost is Oct 9, for a typical growing season of 164 days. For a 90% chance that the last frost has passed, wait until May 8. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- Apr 26Last spring frost (median)50% chance of 32°F after this date
- May 8Safer planting date10% chance of 32°F after this date
- Oct 9First fall frost (median)50% chance of 32°F by this date
- 164 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 22 | May 4 | May 17 |
| 32°F | Apr 12 | Apr 26 | May 8 |
| 28°F | Apr 1 | Apr 15 | Apr 29 |
| 24°F | Mar 22 | Apr 6 | Apr 21 |
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 16 | Sep 29 | Oct 13 |
| 32°F | Sep 23 | Oct 9 | Oct 24 |
| 28°F | Oct 3 | Oct 21 | Nov 2 |
| 24°F | Oct 16 | Oct 30 | Nov 11 |
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 | 128 days | 147 days | 165 days |
| 32°F | 144 days | 164 days | 185 days |
| 28°F | 164 days | 185 days | 206 days |
| 24°F | 185 days | 206 days | 226 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 |
|---|---|---|---|
| 50129 | 5b | -15 to -10°F | 2 km |
| 51462 | 5a | -20 to -15°F | 13 km |
| 50107 | 5a | -20 to -15°F | 15 km |
| 50026 | 5a | -20 to -15°F | 17 km |
| 50064 | 5a | -20 to -15°F | 18 km |
| 50050 | 5a | -20 to -15°F | 19 km |
| 50217 | 5a | -20 to -15°F | 23 km |
| 50544 | 5a | -20 to -15°F | 33 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 USC00134228, at 42.0103, -94.3953, elevation 322 m (1,055 ft).
- Data quality: Standard (24+ years of data), 25 years of freeze data.
- Average days per year at or below 32°F: 149.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Perry (30 km)
- Carroll (38 km)
- Guthrie Center (39 km)
- Boone (42 km)
- Rockwell City (47 km)
- Ames 8 WSW (51 km)
- Audubon (55 km)
- Des Moines Wsfo-Johnston (63 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.