When to plant in St. Charles, IL
USDA Zone 5bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for St. Charles, Illinois — all computed from St. Charles's nearest NOAA weather station.
In zone 5b, St. Charles gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
WEST CHICAGO DUPAGE AP · 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 St. Charles’s own odds, recorded at WEST CHICAGO DUPAGE AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 24 | May 6 | Apr 23 | Sep 25 | Oct 7 | Oct 20 |
| 32°F | May 12 | Apr 25 | Apr 11 | Oct 5 | Oct 19 | Oct 30 |
| 28°F | Apr 29 | Apr 14 | Mar 31 | Oct 16 | 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 St. Charles, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 16 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.
St. Charles planting FAQ
When is the last spring frost in St. Charles, IL?
On average, the last spring frost in St. Charles is around April 25 (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 St. Charles, IL?
Expect St. Charles's first fall frost near October 19 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is St. Charles in?
St. Charles 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 St. Charles?
St. Charles has about 177 frost-free days — a moderate growing season — between the average last spring frost (April 25) and first fall frost (October 19).
When should I plant tomatoes in St. Charles?
For St. Charles, sow tomatoes indoors about February 28–March 14 and move the seedlings out around May 2, after the last spring frost.
Never miss a window in St. Charles
An email when it’s time to start seeds, transplant, and sow — timed to St. Charles’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Geneva · 4 km
- South Elgin · 8 km
- West Chicago · 8 km
- Batavia · 8 km
- Campton Hills · 9 km
- Bartlett · 12 km
- North Aurora · 13 km
- Elgin · 13 km
Frost dates recorded at WEST CHICAGO DUPAGE AP, 5 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 St. Charles, IL — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00094892. Retrieved from https://blissgarden.com/illinois/st-charles.