Frost dates for Marengo, IL
At Marengo, 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 166 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 28Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 12First fall frost (median)50% chance of 32°F by this date
- 166 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 26 | May 10 | May 26 |
| 32°F | Apr 15 | Apr 28 | May 14 |
| 28°F | Apr 3 | Apr 18 | May 4 |
| 24°F | Mar 20 | Apr 6 | 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 21 | Oct 3 | Oct 16 |
| 32°F | Sep 28 | Oct 12 | Oct 27 |
| 28°F | Oct 7 | Oct 25 | Nov 6 |
| 24°F | Oct 21 | Nov 4 | Nov 19 |
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 | 125 days | 145 days | 165 days |
| 32°F | 146 days | 166 days | 187 days |
| 28°F | 165 days | 188 days | 209 days |
| 24°F | 188 days | 211 days | 233 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 |
|---|---|---|---|
| 60152 | 5b | -15 to -10°F | 3 km |
| 60180 | 5b | -15 to -10°F | 8 km |
| 61038 | 5b | -15 to -10°F | 11 km |
| 60135 | 5b | -15 to -10°F | 18 km |
| 60033 | 5b | -15 to -10°F | 18 km |
| 61008 | 5b | -15 to -10°F | 19 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 USC00115326, at 42.2636, -88.6078, elevation 248 m (815 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 147.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Crystal Lake 4nw (17 km)
- Mc Henry -Wg Stratton L&d (30 km)
- Elgin (35 km)
- De Kalb (39 km)
- Barrington 3sw (40 km)
- Rockford Gtr Rockford Airport (41 km)
- Mundelein 4 WSW (44 km)
- Streamwood (44 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.