Last spring frost
Apr 19
Frost Dates for Bourbonnais, IL
First fall frost
Oct 24
Growing season
188 days
Hardiness zone
5b
In an average year around Bourbonnais, IL, the last spring frost (32°F) is about Apr 19 and the first fall frost is about Oct 24, giving roughly a 188-day growing season. To be safe most years, wait until Apr 5 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | May 14 | Apr 30 | Apr 16 |
| Freeze (32°F) | May 3 | Apr 19 | Apr 5 |
| Hard (28°F) | Apr 22 | Apr 6 | Mar 21 |
| Severe (24°F) | Apr 10 | Mar 27 | Mar 11 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 14 | May 9 | May 5 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 20 | Apr 16 |
| 32°F | May 3 | Apr 28 | Apr 25 | Apr 22 | Apr 19 | Apr 16 | Apr 13 | Apr 10 | Apr 5 |
| 28°F | Apr 22 | Apr 17 | Apr 13 | Apr 8 | Apr 6 | Apr 3 | Apr 1 | Mar 28 | Mar 21 |
| 24°F | Apr 10 | Apr 5 | Apr 2 | Mar 31 | Mar 27 | Mar 23 | Mar 20 | Mar 16 | Mar 11 |
| 20°F | Apr 2 | Mar 29 | Mar 24 | Mar 20 | Mar 17 | Mar 13 | Mar 10 | Mar 6 | Feb 28 |
| 16°F | Mar 23 | Mar 18 | Mar 13 | Mar 10 | Mar 7 | Mar 4 | Mar 1 | Feb 26 | Feb 19 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 1 | Oct 14 | Oct 27 |
| Freeze (32°F) | Oct 12 | Oct 24 | Nov 5 |
| Hard (28°F) | Oct 23 | Nov 4 | Nov 19 |
| Severe (24°F) | Nov 1 | Nov 15 | Nov 30 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 5 | Oct 9 | Oct 12 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 27 |
| 32°F | Oct 12 | Oct 17 | Oct 20 | Oct 22 | Oct 24 | Oct 27 | Oct 29 | Nov 1 | Nov 5 |
| 28°F | Oct 23 | Oct 27 | Oct 31 | Nov 1 | Nov 4 | Nov 6 | Nov 11 | Nov 14 | Nov 19 |
| 24°F | Nov 1 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 18 | Nov 21 | Nov 25 | Nov 30 |
| 20°F | Nov 8 | Nov 13 | Nov 17 | Nov 21 | Nov 24 | Nov 28 | Dec 1 | Dec 5 | Dec 11 |
| 16°F | Nov 16 | Nov 22 | Nov 26 | Nov 30 | Dec 2 | Dec 6 | Dec 10 | Dec 16 | Dec 22 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Kankakee Metro Wastewater, Il, about 3.5 miles away@if(!empty($station['elevation_ft'])), at 600 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Bourbonnais, IL?
On average, the last spring frost (32°F) around Bourbonnais, IL is about Apr 19. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 5.
When is the first frost in the fall?
The first fall frost around Bourbonnais, IL typically arrives about Oct 24. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Apr 19 on average, or Apr 5 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 188 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 60914 Planting calendar → Illinois frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026