Last spring frost
Apr 3
Frost Dates for St. Elmo, IL
First fall frost
Oct 24
Growing season
202 days
Hardiness zone
6b
In an average year around St. Elmo, IL, the last spring frost (32°F) is about Apr 3 and the first fall frost is about Oct 24, giving roughly a 202-day growing season. To be safe most years, wait until Mar 19 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 9 | Apr 18 | Mar 31 |
| Freeze (32°F) | Apr 25 | Apr 3 | Mar 19 |
| Hard (28°F) | Apr 13 | Mar 27 | Mar 10 |
| Severe (24°F) | Apr 2 | Mar 17 | Feb 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 9 | May 1 | Apr 26 | Apr 21 | Apr 18 | Apr 13 | Apr 9 | Apr 5 | Mar 31 |
| 32°F | Apr 25 | Apr 18 | Apr 12 | Apr 7 | Apr 3 | Apr 1 | Mar 29 | Mar 25 | Mar 19 |
| 28°F | Apr 13 | Apr 6 | Apr 1 | Mar 30 | Mar 27 | Mar 24 | Mar 21 | Mar 17 | Mar 10 |
| 24°F | Apr 2 | Mar 28 | Mar 24 | Mar 21 | Mar 17 | Mar 14 | Mar 10 | Mar 5 | Feb 28 |
| 20°F | Mar 25 | Mar 19 | Mar 15 | Mar 12 | Mar 7 | Mar 4 | Mar 1 | Feb 26 | Feb 18 |
| 16°F | Mar 17 | Mar 12 | Mar 7 | Mar 3 | Feb 28 | Feb 25 | Feb 19 | Feb 12 | Feb 6 |
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) | Sep 27 | Oct 13 | Oct 28 |
| Freeze (32°F) | Oct 9 | Oct 24 | Nov 8 |
| Hard (28°F) | Oct 21 | Nov 4 | Nov 25 |
| Severe (24°F) | Nov 1 | Nov 16 | Dec 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 27 | Oct 2 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 28 |
| 32°F | Oct 9 | Oct 15 | Oct 19 | Oct 22 | Oct 24 | Oct 27 | Oct 30 | Nov 2 | Nov 8 |
| 28°F | Oct 21 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 12 | Nov 17 | Nov 25 |
| 24°F | Nov 1 | Nov 5 | Nov 8 | Nov 12 | Nov 16 | Nov 22 | Nov 27 | Dec 2 | Dec 7 |
| 20°F | Nov 9 | Nov 14 | Nov 19 | Nov 25 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 19 |
| 16°F | Nov 16 | Nov 23 | Nov 28 | Dec 2 | Dec 7 | Dec 12 | Dec 17 | Dec 22 | Dec 29 |
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: Brownstown 4 Sw, Il, about 7.4 miles away@if(!empty($station['elevation_ft'])), at 530 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 St. Elmo, IL?
On average, the last spring frost (32°F) around St. Elmo, IL is about Apr 3. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 19.
When is the first frost in the fall?
The first fall frost around St. Elmo, 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 3 on average, or Mar 19 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 202 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 62458 Planting calendar → Illinois frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026