Frost dates for 61920Charleston, IL
The average last spring frost in Charleston is April 15 and the average first fall frost is October 23, giving a typical growing season of about 187 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 15
- Average first fall frost
- Oct 23
- Growing season
- 187 days
Safer after May 3 (1-in-10 risk)
Possible by Oct 9 (1-in-10 risk)
Last frost typically in 168 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 13 · Apr 27 · May 15 | Sep 29 · Oct 12 · Oct 25 | 165 days | 100% |
| Frost / freeze (32°F) | Apr 1 · Apr 15 · May 3 | Oct 9 · Oct 23 · Nov 4 | 187 days | 100% |
| Hard freeze (28°F) | Mar 20 · Apr 3 · Apr 20 | Oct 19 · Nov 2 · Nov 16 | 213 days | 100% |
Planting calendar for Charleston
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 15 – May 21 |
| Tomatoes | Transplant outdoors | May 1 – Jul 3 |
| Peppers | Start seeds indoors | Mar 15 – Apr 15 |
| Peppers | Transplant outdoors | May 15 – Jun 15 |
| Eggplant | Start seeds indoors | Apr 1 – Apr 30 |
| Eggplant | Transplant outdoors | May 15 – Jun 15 |
| Cucumbers | Sow outdoors | May 15 – Jul 13 |
| Summer squash | Sow outdoors | May 1 – Jun 15 |
| Winter squash & pumpkins | Sow outdoors | May 15 – Jun 15 |
| Snap beans | Sow outdoors | May 1 – Aug 5 |
| Sweet corn | Sow outdoors | May 1 – Jul 3 |
| Watermelon & cantaloupe | Sow outdoors | May 15 – Jun 15 |
| Okra | Sow outdoors | May 8 – May 31 |
| Peas | Sow outdoors (spring) | Mar 15 – Apr 30 |
| Potatoes | Plant outdoors (spring) | Mar 15 – May 15 |
| Onions | Start seeds indoors (spring) | Feb 1 – Feb 28 |
| Onions | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (spring) | Feb 25 – Mar 31 |
| Broccoli | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (fall) | Jun 23 – Jul 3 |
| Broccoli | Transplant outdoors (fall) | Jul 23 – Aug 3 |
| Cabbage | Start seeds indoors (spring) | Feb 15 – Mar 15 |
| Cabbage | Transplant outdoors (spring) | Mar 15 – Apr 15 |
| Cabbage | Start seeds indoors (fall) | Jun 13 – Jul 13 |
| Cabbage | Transplant outdoors (fall) | Jul 13 – Aug 13 |
| Leaf lettuce | Sow outdoors (spring) | Mar 15 – May 31 |
| Leaf lettuce | Sow outdoors (fall) | Jul 13 – Aug 29 |
| Spinach | Sow outdoors (spring) | Mar 8 – Apr 21 |
| Spinach | Sow outdoors (fall) | Jul 30 – Sep 3 |
| Radishes | Sow outdoors (spring) | Mar 15 – May 5 |
| Radishes | Sow outdoors (fall) | Jul 13 – Sep 13 |
| Kale | Sow outdoors (spring) | Apr 1 – Apr 21 |
| Kale | Sow outdoors (fall) | Jul 6 – Aug 13 |
| Carrots | Sow outdoors (spring) | Apr 15 – May 31 |
| Carrots | Sow outdoors (fall) | Jun 13 – Jul 29 |
| Garlic | Plant outdoors (fall) | Oct 13 – Nov 13 |
Where these dates come from
ZIP code 61920 is matched to the NOAA station Charleston, IL, 1.5 km away, at 700 ft elevation (5 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Charleston, IL (used) | 700 ft | Apr 15 | Oct 23 |
| Mattoon Coles Co Ap, IL | 721 ft | Apr 15 | Oct 24 |
| Mattoon, IL | 701 ft | Apr 11 | Oct 29 |
| Casey, IL | 620 ft | Apr 14 | Oct 20 |
Frost dates near Charleston
- Lerna, IL 62440 · last Apr 15, first Oct 24
- Ashmore, IL 61912 · last Apr 15, first Oct 23
- Janesville, IL 62435 · last Apr 15, first Oct 24
- Westfield, IL 62474 · last Apr 15, first Oct 23
- Mattoon, IL 61938 · last Apr 15, first Oct 24
- Humboldt, IL 61931 · last Apr 15, first Oct 24
- Trilla, IL 62469 · last Apr 15, first Oct 24
- Kansas, IL 61933 · last Apr 15, first Oct 23
Frequently asked questions
- When is the last frost in Charleston, IL?
- For ZIP code 61920, the average last spring frost (32°F) is April 15, based on NOAA 1991-2020 climate normals for the Charleston, IL weather station. There is a 1-in-10 chance of a frost after May 3.
- When is the first frost in Charleston, IL?
- The average first fall frost (32°F) is October 23. There is a 1-in-10 chance of frost by October 9, so tender plants are at risk from that point on.
- How long is the growing season in 61920?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 187 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.