Last spring frost
Apr 3
Frost Dates for Belknap, IL
First fall frost
Nov 5
Growing season
216 days
Hardiness zone
7a
In an average year around Belknap, IL, the last spring frost (32°F) is about Apr 3 and the first fall frost is about Nov 5, giving roughly a 216-day growing season. To be safe most years, wait until Mar 17 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 2 | Apr 14 | Mar 31 |
| Freeze (32°F) | Apr 21 | Apr 3 | Mar 17 |
| Hard (28°F) | Apr 7 | Mar 22 | Mar 2 |
| Severe (24°F) | Mar 30 | Mar 11 | Feb 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 2 | Apr 27 | Apr 22 | Apr 18 | Apr 14 | Apr 11 | Apr 8 | Apr 5 | Mar 31 |
| 32°F | Apr 21 | Apr 14 | Apr 9 | Apr 6 | Apr 3 | Mar 31 | Mar 27 | Mar 23 | Mar 17 |
| 28°F | Apr 7 | Apr 2 | Mar 30 | Mar 25 | Mar 22 | Mar 19 | Mar 15 | Mar 10 | Mar 2 |
| 24°F | Mar 30 | Mar 23 | Mar 19 | Mar 15 | Mar 11 | Mar 7 | Mar 2 | Feb 26 | Feb 17 |
| 20°F | Mar 20 | Mar 14 | Mar 8 | Mar 3 | Feb 28 | Feb 23 | Feb 16 | Feb 9 | Feb 2 |
| 16°F | Mar 12 | Mar 4 | Feb 27 | Feb 21 | Feb 15 | Feb 9 | Feb 4 | Jan 30 | Jan 20 |
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 13 | Oct 25 | Nov 6 |
| Freeze (32°F) | Oct 23 | Nov 5 | Nov 22 |
| Hard (28°F) | Nov 3 | Nov 17 | Dec 4 |
| Severe (24°F) | Nov 10 | Nov 28 | Dec 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 13 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 6 |
| 32°F | Oct 23 | Oct 27 | Oct 31 | Nov 2 | Nov 5 | Nov 7 | Nov 12 | Nov 15 | Nov 22 |
| 28°F | Nov 3 | Nov 6 | Nov 10 | Nov 14 | Nov 17 | Nov 21 | Nov 25 | Nov 29 | Dec 4 |
| 24°F | Nov 10 | Nov 15 | Nov 21 | Nov 25 | Nov 28 | Dec 1 | Dec 6 | Dec 11 | Dec 18 |
| 20°F | Nov 19 | Nov 26 | Dec 1 | Dec 5 | Dec 10 | Dec 13 | Dec 19 | Dec 24 | Dec 31 |
| 16°F | Nov 30 | Dec 7 | Dec 12 | Dec 18 | Dec 24 | Dec 29 | Jan 1 | Jan 7 | Jan 16 |
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: Grand Chain Dam 53, Il, about 12.2 miles away@if(!empty($station['elevation_ft'])), at 385 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 Belknap, IL?
On average, the last spring frost (32°F) around Belknap, IL is about Apr 3. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 17.
When is the first frost in the fall?
The first fall frost around Belknap, IL typically arrives about Nov 5. 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 17 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 216 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 62908 Planting calendar → Illinois frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026