Frost dates for Onawa 3NW, IA
At Onawa 3NW, the median last spring frost (32°F) is May 1 and the median first fall frost is Oct 3, for a typical growing season of 154 days. For a 90% chance that the last frost has passed, wait until May 13. Nearby ZIP codes are in USDA hardiness zones 5a to 5b.
- May 1Last spring frost (median)50% chance of 32°F after this date
- May 13Safer planting date10% chance of 32°F after this date
- Oct 3First fall frost (median)50% chance of 32°F by this date
- 154 daysGrowing season (median)between 32°F freezes
USDA hardiness zone 5a (-20 to -15°F) · see all zone 5a frost dates
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 28 | May 9 | May 22 |
| 32°F | Apr 19 | May 1 | May 13 |
| 28°F | Apr 9 | Apr 22 | May 6 |
| 24°F | Mar 31 | Apr 13 | Apr 27 |
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 13 | Sep 25 | Oct 8 |
| 32°F | Sep 21 | Oct 3 | Oct 18 |
| 28°F | Sep 27 | Oct 13 | Oct 26 |
| 24°F | Oct 6 | Oct 23 | Nov 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 | 121 days | 138 days | 156 days |
| 32°F | 135 days | 154 days | 172 days |
| 28°F | 153 days | 172 days | 192 days |
| 24°F | 172 days | 191 days | 211 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 |
|---|---|---|---|
| 51040 | 5a | -20 to -15°F | 6 km |
| 51063 | 5a | -20 to -15°F | 9 km |
| 68020 | 5b | -15 to -10°F | 16 km |
| 51026 | 5a | -20 to -15°F | 21 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 USC00136243, at 42.0697, -96.1258, elevation 323 m (1,060 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 151.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Castana Exp. Farm (24 km)
- Little Sioux 2 NW (28 km)
- Mapleton No.2 (30 km)
- Sioux City Gateway Airport (41 km)
- Sioux City Ang (42 km)
- Logan (56 km)
- Battle Creek 3NE (56 km)
- Ida Grove 5NW (62 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.