When to plant in Decatur, IL
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Decatur, Illinois — all computed from Decatur's nearest NOAA weather station.
In zone 6a, Decatur gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
The average first fall frost in Decatur is now 6 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
DECATUR WTP · 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 Decatur’s own odds, recorded at DECATUR WTP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 13 | Apr 26 | Apr 12 | Sep 30 | Oct 14 | Oct 27 |
| 32°F | May 1 | Apr 14 | Apr 1 | Oct 11 | Oct 24 | Nov 5 |
| 28°F | Apr 17 | Apr 3 | Mar 18 | Oct 20 | Nov 3 | Nov 19 |
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 Decatur, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 43 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.
Decatur planting FAQ
When is the last spring frost in Decatur, IL?
Decatur's average last spring frost falls near April 14 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Decatur, IL?
In Decatur, the first 32°F freeze of fall lands around October 24 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Decatur in?
Decatur 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 Decatur?
Decatur has about 193 frost-free days — a moderate growing season — between the average last spring frost (April 14) and first fall frost (October 24).
When should I plant tomatoes in Decatur?
For Decatur, sow tomatoes indoors about February 17–March 3 and move the seedlings out around April 21, after the last spring frost.
Never miss a window in Decatur
An email when it’s time to start seeds, transplant, and sow — timed to Decatur’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Taylorville · 46 km
- Lincoln · 50 km
- Mahomet · 59 km
- Springfield · 61 km
- Champaign · 63 km
- Mattoon · 65 km
- Chatham · 68 km
- Urbana · 69 km
Frost dates recorded at DECATUR WTP, 3 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 Decatur, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00112193. Retrieved from https://blissgarden.com/illinois/decatur.