When to plant in Chatham, IL
USDA Zone 6aChatham, Illinois frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
Zone 6a means Chatham sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
SPRINGFIELD #2 · 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 Chatham’s own odds, recorded at SPRINGFIELD #2.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 13 | Apr 27 | Apr 13 | Sep 29 | Oct 13 | Oct 23 |
| 32°F | Apr 30 | Apr 15 | Apr 3 | Oct 9 | Oct 22 | Nov 2 |
| 28°F | Apr 19 | Apr 5 | Mar 21 | Oct 20 | Nov 1 | Nov 15 |
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 Chatham, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 20 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.
Chatham planting FAQ
When is the last spring frost in Chatham, IL?
On average, the last spring frost in Chatham is around April 15 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Chatham, IL?
In Chatham, the first 32°F freeze of fall lands around October 22 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Chatham in?
Chatham 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 Chatham?
There are roughly 190 frost-free days in Chatham (a moderate growing season), running from the average last frost around April 15 to the first fall frost near October 22.
When should I plant tomatoes in Chatham?
In Chatham, 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 Chatham
An email when it’s time to start seeds, transplant, and sow — timed to Chatham’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Springfield · 14 km
- Taylorville · 35 km
- Jacksonville · 47 km
- Lincoln · 60 km
- Decatur · 68 km
- Godfrey · 92 km
- Alton · 94 km
- Wood River · 96 km
Frost dates recorded at SPRINGFIELD #2, 14 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 Chatham, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00118186. Retrieved from https://blissgarden.com/illinois/chatham.