When to plant in Plainfield, IL
USDA Zone 5bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Plainfield, Illinois — all computed from Plainfield's nearest NOAA weather station.
Zone 5b means Plainfield sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
ROMEOVILLE WFO · 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 Plainfield’s own odds, recorded at ROMEOVILLE WFO.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 17 | May 1 | Apr 17 | Sep 28 | Oct 12 | Oct 24 |
| 32°F | May 6 | Apr 20 | Apr 7 | Oct 7 | Oct 22 | Nov 3 |
| 28°F | Apr 23 | Apr 8 | Mar 27 | Oct 19 | Nov 1 | Nov 15 |
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 Plainfield, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 19 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.
Plainfield planting FAQ
When is the last spring frost in Plainfield, IL?
On average, the last spring frost in Plainfield is around April 20 (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 Plainfield, IL?
Expect Plainfield's first fall frost near October 22 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Plainfield in?
Plainfield 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 Plainfield?
There are roughly 185 frost-free days in Plainfield (a moderate growing season), running from the average last frost around April 20 to the first fall frost near October 22.
When should I plant tomatoes in Plainfield?
In Plainfield, start tomato seeds indoors around February 23–March 9, then transplant seedlings outdoors around April 27 once the danger of frost has passed.
Never miss a window in Plainfield
An email when it’s time to start seeds, transplant, and sow — timed to Plainfield’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Romeoville · 10 km
- Crest Hill · 11 km
- Shorewood · 11 km
- Oswego · 12 km
- Bolingbrook · 13 km
- Joliet · 13 km
- Naperville · 15 km
- Montgomery · 16 km
Frost dates recorded at ROMEOVILLE WFO, 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 Plainfield, IL — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00117457. Retrieved from https://blissgarden.com/illinois/plainfield.