When to plant in Charleston, IL
USDA Zone 6aEverything below — frost dates, hardiness zone, and what to plant when in Charleston, Illinois — is derived from the closest NOAA station with complete climate normals.
Zone 6a means Charleston sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
CHARLESTON · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Charleston’s own odds, recorded at CHARLESTON.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 15 | Apr 27 | Apr 13 | Sep 29 | Oct 12 | Oct 25 |
| 32°F | May 3 | Apr 15 | Apr 1 | Oct 9 | Oct 23 | Nov 4 |
| 28°F | Apr 20 | Apr 3 | Mar 20 | Oct 19 | Nov 2 | Nov 16 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Charleston, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 15 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Charleston planting FAQ
When is the last spring frost in Charleston, IL?
Plan for the last spring frost in Charleston around April 15 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Charleston, IL?
The first fall frost in Charleston typically arrives around October 23 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Charleston in?
Charleston is in USDA hardiness zone 6a. In zone 6a, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Charleston?
There are roughly 191 frost-free days in Charleston (a moderate growing season), running from the average last frost around April 15 to the first fall frost near October 23.
When should I plant tomatoes in Charleston?
In Charleston, start tomato seeds indoors around February 18–March 4, then transplant seedlings outdoors around April 22 once the danger of frost has passed.
Never miss a window in Charleston
An email when it’s time to start seeds, transplant, and sow — timed to Charleston’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at CHARLESTON, 1 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Charleston, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00111436. Retrieved from https://blissgarden.com/illinois/charleston.