When to plant in Westmont, IL
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Westmont, Illinois — all computed from Westmont's nearest NOAA weather station.
Zone 6a means Westmont sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
LISLE-MORTON ARBORETUM · 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 Westmont’s own odds, recorded at LISLE-MORTON ARBORETUM.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 25 | May 9 | Apr 25 | Sep 22 | Oct 6 | Oct 18 |
| 32°F | May 14 | Apr 28 | Apr 14 | Oct 1 | Oct 16 | Oct 29 |
| 28°F | May 4 | Apr 16 | Apr 2 | Oct 12 | Oct 26 | Nov 8 |
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 Westmont, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 12 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.
Westmont planting FAQ
When is the last spring frost in Westmont, IL?
On average, the last spring frost in Westmont is around April 28 (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 Westmont, IL?
In Westmont, the first 32°F freeze of fall lands around October 16 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Westmont in?
Westmont 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 Westmont?
There are roughly 171 frost-free days in Westmont (a moderate growing season), running from the average last frost around April 28 to the first fall frost near October 16.
When should I plant tomatoes in Westmont?
In Westmont, start tomato seeds indoors around March 3–March 17, then transplant seedlings outdoors around May 5 once the danger of frost has passed.
Never miss a window in Westmont
An email when it’s time to start seeds, transplant, and sow — timed to Westmont’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Hinsdale · 4 km
- Downers Grove · 4 km
- Darien · 5 km
- Western Springs · 6 km
- Burr Ridge · 7 km
- La Grange · 8 km
- Woodridge · 9 km
- Westchester · 9 km
Frost dates recorded at LISLE-MORTON ARBORETUM, 9 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 Westmont, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00115097. Retrieved from https://blissgarden.com/illinois/westmont.