When to plant in Mount Prospect, IL
USDA Zone 6aEverything below — frost dates, hardiness zone, and what to plant when in Mount Prospect, Illinois — is derived from the closest NOAA station with complete climate normals.
Zone 6a means Mount Prospect sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
The average last spring frost in Mount Prospect is now 6 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
CHICAGO PALWAUKEE 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 Mount Prospect’s own odds, recorded at CHICAGO PALWAUKEE AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 15 | Apr 30 | Apr 16 | Oct 1 | Oct 16 | Oct 27 |
| 32°F | May 3 | Apr 19 | Apr 4 | Oct 13 | Oct 26 | Nov 9 |
| 28°F | Apr 20 | Apr 5 | Mar 22 | Oct 26 | Nov 7 | Nov 21 |
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 Mount Prospect, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 15 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.
Mount Prospect planting FAQ
When is the last spring frost in Mount Prospect, IL?
On average, the last spring frost in Mount Prospect is around April 19 (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 Mount Prospect, IL?
In Mount Prospect, the first 32°F freeze of fall lands around October 26 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Mount Prospect in?
Mount Prospect 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 Mount Prospect?
There are roughly 190 frost-free days in Mount Prospect (a moderate growing season), running from the average last frost around April 19 to the first fall frost near October 26.
When should I plant tomatoes in Mount Prospect?
In Mount Prospect, start tomato seeds indoors around February 22–March 8, then transplant seedlings outdoors around April 26 once the danger of frost has passed.
Never miss a window in Mount Prospect
An email when it’s time to start seeds, transplant, and sow — timed to Mount Prospect’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Prospect Heights · 4 km
- Des Plaines · 4 km
- Arlington Heights · 5 km
- Rolling Meadows · 7 km
- Wheeling · 7 km
- Elk Grove Village · 8 km
- Glenview · 9 km
- Park Ridge · 10 km
Frost dates recorded at CHICAGO PALWAUKEE AP, 7 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 Mount Prospect, IL — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00004838. Retrieved from https://blissgarden.com/illinois/mount-prospect.