When to plant in Round Lake, IL
USDA Zone 5bEverything below — frost dates, hardiness zone, and what to plant when in Round Lake, Illinois — is derived from the closest NOAA station with complete climate normals.
Zone 5b means Round Lake sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
MUNDELEIN 4 WSW · 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 Round Lake’s own odds, recorded at MUNDELEIN 4 WSW.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 26 | May 10 | Apr 25 | Sep 24 | Oct 9 | Oct 22 |
| 32°F | May 15 | Apr 29 | Apr 14 | Oct 4 | Oct 20 | Nov 1 |
| 28°F | May 4 | Apr 16 | Apr 2 | Oct 16 | Oct 31 | Nov 12 |
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 Round Lake, 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.
Round Lake planting FAQ
When is the last spring frost in Round Lake, IL?
Plan for the last spring frost in Round Lake around April 29 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Round Lake, IL?
The first fall frost in Round Lake typically arrives around October 20 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Round Lake in?
Round Lake is in USDA hardiness zone 5b. In zone 5b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Round Lake?
There are roughly 174 frost-free days in Round Lake (a moderate growing season), running from the average last frost around April 29 to the first fall frost near October 20.
When should I plant tomatoes in Round Lake?
In Round Lake, start tomato seeds indoors around March 4–March 18, then transplant seedlings outdoors around May 6 once the danger of frost has passed.
Never miss a window in Round Lake
An email when it’s time to start seeds, transplant, and sow — timed to Round Lake’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Round Lake Beach · 5 km
- Grayslake · 6 km
- Wauconda · 8 km
- Gages Lake · 10 km
- Lindenhurst · 10 km
- Mundelein · 10 km
- Fox Lake · 12 km
- Libertyville · 13 km
Frost dates recorded at MUNDELEIN 4 WSW, 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 Round Lake, IL — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00115961. Retrieved from https://blissgarden.com/illinois/round-lake.