Frost dates / Illinois / Springfield
Frost dates in Springfield, IL
The station on this page is SPRINGFIELD #2, IL US (USC00118186), 1.8 miles from the city point. Population in the Census 2024 estimate is 112,949.
Zone 6aUSDA average annual extreme minimum -10°F to -5°F, from ZIP 62701 (0.7 miles from the city point used on this page).
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Last 32°F in spring
NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.
| Probability | Date | How to read it |
|---|---|---|
| 90% | April 3 | Earlier date. A last 32°F on or after this day is common. |
| 50% | April 15 | Median. |
| 10% | April 30 | Later date. A last 32°F on or after this day is uncommon. |
First 32°F in fall
NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.
| Probability | Date | How to read it |
|---|---|---|
| 10% | October 9 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | October 22 | Median. |
| 90% | November 2 | Later date. A first 32°F on or before this day is common. |
32°F growing-season length
Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.
| Probability the season is at least this long | Days |
|---|---|
| 10% | 206 |
| 50% | 188 |
| 90% | 169 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | April 19 | April 5 | March 21 |
| First, on or before | October 20 | November 1 | November 15 |
| Season at least | 230 days | 210 days | 191 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | May 13 | April 27 | April 13 |
| First, on or before | September 29 | October 13 | October 23 |
| Season at least | 185 days | 167 days | 147 days |
Station SPRINGFIELD #2, IL US (USC00118186). Completeness flag R, 12 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 182.6 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.
Planting calendar for Springfield · Zone 6a
Check a crop against this station
Springfield, IL
Zone 6aAverage annual extreme minimum -10°F to -5°F
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Illinois. Nearest qualified station: SPRINGFIELD #2, IL US (USC00118186), 1.8 miles. Median last 32°F April 15. Median first 32°F October 22. The 50% growing-season length is 188 days.
Open the ZIP page · Crop guides for Illinois
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | April 30 | April 15 | April 3 |
| First 32°F on or before | October 9 | October 22 | November 2 |
Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.
Planting calendar
Windows below are from University of Illinois Extension, When to Plant, retrieved 2026-10-10. The planting chart is divided into Northern Illinois, Central Illinois, and Southern Illinois. Median dates for the last 32-degree freeze on the same page: Northern Illinois April 8-29; Central Illinois April 8-15; Southern Illinois April 1-8. The page also says southern Illinois can generally start crops two weeks earlier than central Illinois and northern Illinois about two weeks later; the crop rows below are the chart dates, not a recalculation of that sentence.
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