Frost dates for Sigourney, IA
At Sigourney, the median last spring frost (32°F) is Apr 24 and the median first fall frost is Oct 15, for a typical growing season of 172 days. For a 90% chance that the last frost has passed, wait until May 9. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 24Last spring frost (median)50% chance of 32°F after this date
- May 9Safer planting date10% chance of 32°F after this date
- Oct 15First fall frost (median)50% chance of 32°F by this date
- 172 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 20 | May 4 | May 17 |
| 32°F | Apr 9 | Apr 24 | May 9 |
| 28°F | Mar 31 | Apr 12 | Apr 30 |
| 24°F | Mar 18 | Apr 3 | 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 21 | Oct 5 | Oct 17 |
| 32°F | Sep 30 | Oct 15 | Oct 27 |
| 28°F | Oct 12 | Oct 24 | Nov 4 |
| 24°F | Oct 21 | Nov 1 | Nov 15 |
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 | 135 days | 151 days | 169 days |
| 32°F | 152 days | 172 days | 191 days |
| 28°F | 172 days | 194 days | 211 days |
| 24°F | 192 days | 212 days | 231 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 |
|---|---|---|---|
| 52591 | 5b | -15 to -10°F | 4 km |
| 52562 | 5b | -15 to -10°F | 8 km |
| 52550 | 5b | -15 to -10°F | 11 km |
| 50268 | 5b | -15 to -10°F | 14 km |
| 52355 | 5b | -15 to -10°F | 14 km |
| 52231 | 5b | -15 to -10°F | 14 km |
| 50136 | 5b | -15 to -10°F | 16 km |
| 50255 | 5b | -15 to -10°F | 16 km |
| 52576 | 5b | -15 to -10°F | 17 km |
| 52568 | 5b | -15 to -10°F | 18 km |
| 52335 | 5b | -15 to -10°F | 21 km |
| 50104 | 5b | -15 to -10°F | 22 km |
| 52222 | 5b | -15 to -10°F | 28 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 USC00137678, at 41.3372, -92.2278, elevation 223 m (732 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 142.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ottumwa Industrial Airport (31 km)
- Oskaloosa (35 km)
- Williamsburg 1e (41 km)
- Fairfield (42 km)
- Washington (44 km)
- Albia 3 NNE (56 km)
- Belle Plaine (61 km)
- Grinnell 3 SW (61 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.