When to plant in Troy, IL
USDA Zone 7aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Troy, Illinois — all computed from Troy's nearest NOAA weather station.
Troy's nearest full-normals station sits about 23 km out, so treat these as a close estimate — local microclimate can nudge your first and last frost. In zone 7a, Troy supports a wide range of perennials year-round; the frost dates above are what set your annual vegetable timing.
The average first fall frost in Troy is now 5 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
BELLEVILLE SIU RSCH · 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 Troy’s own odds, recorded at BELLEVILLE SIU RSCH.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 8 | Apr 23 | Apr 10 | Sep 27 | Oct 9 | Oct 23 |
| 32°F | Apr 28 | Apr 12 | Mar 28 | Oct 3 | Oct 20 | Nov 1 |
| 28°F | Apr 16 | Mar 31 | Mar 14 | Oct 15 | Oct 30 | 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 Troy, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 29 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.
Troy planting FAQ
When is the last spring frost in Troy, IL?
Troy's average last spring frost falls near April 12 — 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 Troy, IL?
In Troy, the first 32°F freeze of fall lands around October 20 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Troy in?
Troy is in USDA hardiness zone 7a. In zone 7a, winters are moderate — most common vegetables grow well in season.
How long is the growing season in Troy?
Troy has about 191 frost-free days — a moderate growing season — between the average last spring frost (April 12) and first fall frost (October 20).
When should I plant tomatoes in Troy?
For Troy, sow tomatoes indoors about February 15–March 1 and move the seedlings out around April 19, after the last spring frost.
Never miss a window in Troy
An email when it’s time to start seeds, transplant, and sow — timed to Troy’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Glen Carbon · 9 km
- Edwardsville · 11 km
- Collinsville · 11 km
- O'Fallon · 14 km
- Fairview Heights · 17 km
- Highland · 19 km
- Shiloh · 19 km
- Granite City · 20 km
Frost dates recorded at BELLEVILLE SIU RSCH, 23 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 Troy, IL — Frost Dates & Zone 7a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00013802. Retrieved from https://blissgarden.com/illinois/troy.