Frost dates for Allison, IA
At Allison, the median last spring frost (32°F) is Apr 27 and the median first fall frost is Oct 8, for a typical growing season of 165 days. For a 90% chance that the last frost has passed, wait until May 8. Nearby ZIP codes are in USDA hardiness zone 5a.
- Apr 27Last spring frost (median)50% chance of 32°F after this date
- May 8Safer planting date10% chance of 32°F after this date
- Oct 8First fall frost (median)50% chance of 32°F by this date
- 165 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 23 | May 5 | May 16 |
| 32°F | Apr 12 | Apr 27 | May 8 |
| 28°F | Apr 2 | Apr 16 | Apr 30 |
| 24°F | Mar 22 | Apr 6 | Apr 22 |
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 17 | Sep 30 | Oct 12 |
| 32°F | Sep 24 | Oct 8 | Oct 22 |
| 28°F | Oct 4 | Oct 20 | Nov 1 |
| 24°F | Oct 15 | Oct 29 | Nov 10 |
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 | 129 days | 147 days | 165 days |
| 32°F | 146 days | 165 days | 186 days |
| 28°F | 166 days | 185 days | 203 days |
| 24°F | 185 days | 204 days | 224 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 |
|---|---|---|---|
| 50602 | 5a | -20 to -15°F | 1 km |
| 50611 | 5a | -20 to -15°F | 12 km |
| 50619 | 5a | -20 to -15°F | 12 km |
| 50625 | 5a | -20 to -15°F | 15 km |
| 50636 | 5a | -20 to -15°F | 16 km |
| 50670 | 5a | -20 to -15°F | 17 km |
| 50604 | 5a | -20 to -15°F | 19 km |
| 50665 | 5a | -20 to -15°F | 19 km |
| 50608 | 5a | -20 to -15°F | 23 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 USC00130157, at 42.7536, -92.8022, elevation 316 m (1,038 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 150.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Hampton (33 km)
- Charles City (36 km)
- Waterloo Muni Airport (40 km)
- Grundy Center (43 km)
- Tripoli (45 km)
- Iowa Falls (45 km)
- Eldora (49 km)
- New Hampton (51 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.