When to plant in Algonquin, IL
USDA Zone 5bEverything below — frost dates, hardiness zone, and what to plant when in Algonquin, Illinois — is derived from the closest NOAA station with complete climate normals.
Zone 5b means Algonquin sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
ELGIN · 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 Algonquin’s own odds, recorded at ELGIN.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 24 | May 6 | Apr 22 | Sep 24 | Oct 7 | Oct 21 |
| 32°F | May 12 | Apr 26 | Apr 12 | Oct 3 | Oct 18 | Oct 31 |
| 28°F | Apr 29 | Apr 14 | Apr 1 | Oct 15 | Oct 29 | 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 Algonquin, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 14 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.
Algonquin planting FAQ
When is the last spring frost in Algonquin, IL?
On average, the last spring frost in Algonquin is around April 26 (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 Algonquin, IL?
In Algonquin, the first 32°F freeze of fall lands around October 18 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Algonquin in?
Algonquin 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 Algonquin?
There are roughly 175 frost-free days in Algonquin (a moderate growing season), running from the average last frost around April 26 to the first fall frost near October 18.
When should I plant tomatoes in Algonquin?
In Algonquin, 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 Algonquin
An email when it’s time to start seeds, transplant, and sow — timed to Algonquin’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Lake in the Hills · 2 km
- Carpentersville · 5 km
- Crystal Lake · 8 km
- Cary · 8 km
- Huntley · 9 km
- Pingree Grove · 12 km
- Elgin · 13 km
- Barrington · 16 km
Frost dates recorded at ELGIN, 11 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 Algonquin, IL — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00112736. Retrieved from https://blissgarden.com/illinois/algonquin.