Frost dates for Unionville, MO
At Unionville, the median last spring frost (32°F) is Apr 17 and the median first fall frost is Oct 22, for a typical growing season of 186 days. For a 90% chance that the last frost has passed, wait until Apr 30. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 17Last spring frost (median)50% chance of 32°F after this date
- Apr 30Safer planting date10% chance of 32°F after this date
- Oct 22First fall frost (median)50% chance of 32°F by this date
- 186 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 14 | Apr 28 | May 9 |
| 32°F | Apr 4 | Apr 17 | Apr 30 |
| 28°F | Mar 25 | Apr 8 | Apr 22 |
| 24°F | Mar 13 | Mar 31 | Apr 14 |
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 27 | Oct 11 | Oct 24 |
| 32°F | Oct 7 | Oct 22 | Nov 1 |
| 28°F | Oct 19 | Oct 31 | Nov 12 |
| 24°F | Oct 26 | Nov 6 | Nov 21 |
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 | 146 days | 165 days | 183 days |
| 32°F | 168 days | 186 days | 203 days |
| 28°F | 185 days | 205 days | 223 days |
| 24°F | 203 days | 222 days | 242 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 |
|---|---|---|---|
| 63565 | 5b | -15 to -10°F | 5 km |
| 64655 | 5b | -15 to -10°F | 22 km |
| 63551 | 5b | -15 to -10°F | 22 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 USC00238523, at 40.4750, -93.0031, elevation 323 m (1,060 ft).
- Data quality: Representative (10+ years), 18 years of freeze data.
- Average days per year at or below 32°F: 134.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Green City 5n (15 km)
- Kirksville (47 km)
- Princeton (50 km)
- Kirksville Regional Airport (57 km)
- Spickard 7 W (65 km)
- Trenton (67 km)
- Chillicothe 22 ENE (69 km)
- Memphis (69 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.