Frost dates for Knox Wastewater Plant, IN
At Knox Wastewater Plant, the median last spring frost (32°F) is Apr 26 and the median first fall frost is Oct 19, for a typical growing season of 174 days. For a 90% chance that the last frost has passed, wait until May 12. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 26Last spring frost (median)50% chance of 32°F after this date
- May 12Safer planting date10% chance of 32°F after this date
- Oct 19First fall frost (median)50% chance of 32°F by this date
- 174 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 6 | May 24 |
| 32°F | Apr 12 | Apr 26 | May 12 |
| 28°F | Apr 1 | Apr 15 | Apr 30 |
| 24°F | Mar 17 | Apr 2 | Apr 18 |
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 25 | Oct 8 | Oct 21 |
| 32°F | Oct 5 | Oct 19 | Oct 31 |
| 28°F | Oct 15 | Oct 30 | Nov 12 |
| 24°F | Oct 30 | Nov 11 | Nov 26 |
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 | 132 days | 153 days | 172 days |
| 32°F | 154 days | 174 days | 194 days |
| 28°F | 177 days | 198 days | 218 days |
| 24°F | 203 days | 222 days | 243 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 |
|---|---|---|---|
| 46534 | 5b | -15 to -10°F | 2 km |
| 46531 | 5b | -15 to -10°F | 11 km |
| 46532 | 5b | -15 to -10°F | 12 km |
| 46340 | 5b | -15 to -10°F | 15 km |
| 46366 | 5b | -15 to -10°F | 15 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 USC00124657, at 41.3053, -86.6286, elevation 210 m (690 ft).
- Data quality: Representative (10+ years), 12 years of freeze data.
- Average days per year at or below 32°F: 137.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Plymouth (25 km)
- Wanatah 2 WNW (29 km)
- Winamac 2sse (31 km)
- Laporte (35 km)
- Valparaiso Porter Co Muni Airport (35 km)
- Wheatfield (38 km)
- Lakeville (39 km)
- Valparaiso Wtr Wks (41 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.