When to plant in Lemont, IL
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Lemont, Illinois — all computed from Lemont's nearest NOAA weather station.
Zone 6a means Lemont sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
LITTLE RED SCHOOL HSE · 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 Lemont’s own odds, recorded at LITTLE RED SCHOOL HSE.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 18 | Apr 30 | Apr 16 | Sep 28 | Oct 12 | Oct 24 |
| 32°F | May 5 | Apr 19 | Apr 6 | Oct 8 | Oct 22 | Nov 3 |
| 28°F | Apr 22 | Apr 7 | Mar 26 | Oct 19 | Nov 1 | 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 Lemont, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 18 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.
Lemont planting FAQ
When is the last spring frost in Lemont, IL?
Lemont's average last spring frost falls near April 19 — 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 Lemont, IL?
Expect Lemont's first fall frost near October 22 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Lemont in?
Lemont 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 Lemont?
There are roughly 186 frost-free days in Lemont (a moderate growing season), running from the average last frost around April 19 to the first fall frost near October 22.
When should I plant tomatoes in Lemont?
In Lemont, start tomato seeds indoors around February 22–March 8, then transplant seedlings outdoors around April 26 once the danger of frost has passed.
Never miss a window in Lemont
An email when it’s time to start seeds, transplant, and sow — timed to Lemont’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Homer Glen · 7 km
- Darien · 9 km
- Woodridge · 9 km
- Lockport · 9 km
- Bolingbrook · 10 km
- Burr Ridge · 10 km
- Romeoville · 11 km
- Orland Park · 12 km
Frost dates recorded at LITTLE RED SCHOOL HSE, 10 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 Lemont, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00115110. Retrieved from https://blissgarden.com/illinois/lemont.