Frost dates for Illinois City Dam 16, IL
At Illinois City Dam 16, the median last spring frost (32°F) is Apr 18 and the median first fall frost is Oct 24, for a typical growing season of 188 days. For a 90% chance that the last frost has passed, wait until May 2. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 18Last spring frost (median)50% chance of 32°F after this date
- May 2Safer planting date10% chance of 32°F after this date
- Oct 24First fall frost (median)50% chance of 32°F by this date
- 188 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 16 | Apr 29 | May 11 |
| 32°F | Apr 5 | Apr 18 | May 2 |
| 28°F | Mar 25 | Apr 8 | Apr 25 |
| 24°F | Mar 9 | Mar 30 | Apr 13 |
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 | Oct 1 | Oct 15 | Oct 27 |
| 32°F | Oct 11 | Oct 24 | Nov 6 |
| 28°F | Oct 21 | Nov 1 | Nov 15 |
| 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 | 150 days | 169 days | 188 days |
| 32°F | 168 days | 188 days | 207 days |
| 28°F | 189 days | 208 days | 228 days |
| 24°F | 207 days | 229 days | 250 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 |
|---|---|---|---|
| 61259 | 5b | -15 to -10°F | 8 km |
| 61237 | 5b | -15 to -10°F | 15 km |
| 52759 | 5b | -15 to -10°F | 17 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 USC00114355, at 41.4256, -91.0094, elevation 168 m (550 ft).
- Data quality: Representative (10+ years), 11 years of freeze data.
- Average days per year at or below 32°F: 131.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- New Boston Dam 17 (26 km)
- Aledo (34 km)
- Rock Island L&d 15 (38 km)
- Moline Quad City Intl Airport (41 km)
- Monmouth 4nw (60 km)
- Gladstone Dam 18 (60 km)
- Monmouth (62 km)
- Geneseo (72 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.