Frost dates for Spencer Muni Airport, IA
At Spencer Muni Airport, the median last spring frost (32°F) is May 2 and the median first fall frost is Oct 2, for a typical growing season of 154 days. For a 90% chance that the last frost has passed, wait until May 15. Nearby ZIP codes are in USDA hardiness zone 5a.
- May 2Last spring frost (median)50% chance of 32°F after this date
- May 15Safer planting date10% chance of 32°F after this date
- Oct 2First fall frost (median)50% chance of 32°F by this date
- 154 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 28 | May 9 | May 22 |
| 32°F | Apr 17 | May 2 | May 15 |
| 28°F | Apr 8 | Apr 22 | May 7 |
| 24°F | Mar 29 | Apr 12 | 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 9 | Sep 24 | Oct 7 |
| 32°F | Sep 18 | Oct 2 | Oct 16 |
| 28°F | Sep 26 | Oct 12 | Oct 27 |
| 24°F | Oct 5 | Oct 23 | Nov 5 |
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 | 118 days | 136 days | 155 days |
| 32°F | 134 days | 154 days | 173 days |
| 28°F | 152 days | 172 days | 193 days |
| 24°F | 170 days | 193 days | 214 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 |
|---|---|---|---|
| 51338 | 5a | -20 to -15°F | 11 km |
| 51357 | 5a | -20 to -15°F | 13 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 USW00014972, at 43.1644, -95.2017, elevation 408 m (1,338 ft).
- Data quality: Representative (10+ years), 24 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
- Spencer 1 N (4 km)
- Milford 4 NW (24 km)
- Spirit Lake (29 km)
- Sioux Rapids 4 E (32 km)
- Lake Park (33 km)
- Primghar (36 km)
- Sanborn (37 km)
- Emmetsburg (43 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.