When to plant in Lake Forest, IL
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Lake Forest, Illinois — all computed from Lake Forest's nearest NOAA weather station.
Zone 6a means Lake Forest sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
CHICAGO BOTANIC GARDEN · 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 Lake Forest’s own odds, recorded at CHICAGO BOTANIC GARDEN.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 26 | May 8 | Apr 24 | Sep 28 | Oct 10 | Oct 24 |
| 32°F | May 11 | Apr 26 | Apr 11 | Oct 5 | Oct 21 | Nov 2 |
| 28°F | Apr 28 | Apr 13 | Mar 31 | Oct 17 | Nov 1 | Nov 14 |
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 Lake Forest, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 13 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.
Lake Forest planting FAQ
When is the last spring frost in Lake Forest, IL?
Lake Forest's average last spring frost falls near April 26 — 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 Lake Forest, IL?
Expect Lake Forest's first fall frost near October 21 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Lake Forest in?
Lake Forest 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 Lake Forest?
There are roughly 178 frost-free days in Lake Forest (a moderate growing season), running from the average last frost around April 26 to the first fall frost near October 21.
When should I plant tomatoes in Lake Forest?
In Lake Forest, start tomato seeds indoors around March 1–March 15, then transplant seedlings outdoors around May 3 once the danger of frost has passed.
Never miss a window in Lake Forest
An email when it’s time to start seeds, transplant, and sow — timed to Lake Forest’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Highland Park · 7 km
- Deerfield · 8 km
- Vernon Hills · 9 km
- North Chicago · 9 km
- Libertyville · 11 km
- Buffalo Grove · 12 km
- Northbrook · 12 km
- Wheeling · 13 km
Frost dates recorded at CHICAGO BOTANIC GARDEN, 12 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 Lake Forest, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00111497. Retrieved from https://blissgarden.com/illinois/lake-forest.