Frost dates for Altona, IL
At Altona, the median last spring frost (32°F) is Apr 28 and the median first fall frost is Oct 12, for a typical growing season of 165 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 28Last spring frost (median)50% chance of 32°F after this date
- May 12Safer planting date10% chance of 32°F after this date
- Oct 12First fall frost (median)50% chance of 32°F by this date
- 165 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 25 | May 7 | May 20 |
| 32°F | Apr 15 | Apr 28 | May 12 |
| 28°F | Apr 5 | Apr 18 | May 3 |
| 24°F | Mar 25 | Apr 8 | Apr 22 |
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 19 | Oct 1 | Oct 15 |
| 32°F | Sep 28 | Oct 12 | Oct 26 |
| 28°F | Oct 8 | Oct 22 | Nov 3 |
| 24°F | Oct 19 | Nov 1 | Nov 13 |
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 | 130 days | 147 days | 165 days |
| 32°F | 146 days | 165 days | 186 days |
| 28°F | 165 days | 185 days | 203 days |
| 24°F | 185 days | 204 days | 226 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 |
|---|---|---|---|
| 61414 | 5b | -15 to -10°F | 1 km |
| 61467 | 5b | -15 to -10°F | 9 km |
| 61490 | 5b | -15 to -10°F | 11 km |
| 61485 | 5b | -15 to -10°F | 13 km |
| 61413 | 5b | -15 to -10°F | 19 km |
| 61262 | 5b | -15 to -10°F | 23 km |
| 61468 | 5b | -15 to -10°F | 24 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 USC00110140, at 41.1203, -90.1642, elevation 233 m (765 ft).
- Data quality: Representative (10+ years), 14 years of freeze data.
- Average days per year at or below 32°F: 144.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Galva (12 km)
- Kewanee 1 E (26 km)
- Knoxville (26 km)
- Galesburg (27 km)
- Geneseo (37 km)
- Princeville (40 km)
- Monmouth (44 km)
- Moline Quad City Intl Airport (49 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.