Frost dates for Swea City 5n, IA
At Swea City 5n, the median last spring frost (32°F) is May 4 and the median first fall frost is Oct 1, for a typical growing season of 150 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 4Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 1First fall frost (median)50% chance of 32°F by this date
- 150 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 | May 1 | May 11 | May 24 |
| 32°F | Apr 21 | May 4 | May 14 |
| 28°F | Apr 9 | Apr 25 | May 6 |
| 24°F | Mar 31 | Apr 14 | Apr 29 |
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 11 | Sep 23 | Oct 6 |
| 32°F | Sep 18 | Oct 1 | Oct 15 |
| 28°F | Sep 26 | Oct 10 | Oct 24 |
| 24°F | Oct 7 | Oct 22 | Nov 4 |
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 | 119 days | 134 days | 151 days |
| 32°F | 133 days | 150 days | 167 days |
| 28°F | 149 days | 168 days | 189 days |
| 24°F | 170 days | 190 days | 210 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 |
|---|---|---|---|
| 50590 | 5a | -20 to -15°F | 5 km |
| 50556 | 5a | -20 to -15°F | 9 km |
| 50514 | 5a | -20 to -15°F | 14 km |
| 56027 | 5a | -20 to -15°F | 17 km |
| 50517 | 5a | -20 to -15°F | 18 km |
| 50451 | 5a | -20 to -15°F | 19 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 USC00138026, at 43.4542, -94.3069, elevation 360 m (1,180 ft).
- Data quality: Representative (10+ years), 29 years of freeze data.
- Average days per year at or below 32°F: 163.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Estherville Muni Airport (36 km)
- Estherville 4e (36 km)
- Algona (44 km)
- Emmetsburg (50 km)
- Forest City 2 NNE (58 km)
- Britt 3e (60 km)
- Spirit Lake (67 km)
- Milford 4 NW (71 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.