When to plant in Four Square Mile, CO
USDA Zone 6aEverything below — frost dates, hardiness zone, and what to plant when in Four Square Mile, Colorado — is derived from the closest NOAA station with complete climate normals.
Zone 6a means Four Square Mile sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
CHERRY CREEK DAM · 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 Four Square Mile’s own odds, recorded at CHERRY CREEK DAM.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 1 | May 18 | May 7 | Sep 18 | Sep 30 | Oct 12 |
| 32°F | May 21 | May 7 | Apr 26 | Sep 25 | Oct 8 | Oct 19 |
| 28°F | May 10 | Apr 29 | Apr 11 | Sep 30 | Oct 15 | Oct 27 |
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 Four Square Mile, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 12 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.
Four Square Mile planting FAQ
When is the last spring frost in Four Square Mile, CO?
Plan for the last spring frost in Four Square Mile around May 7 (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 Four Square Mile, CO?
Expect Four Square Mile's first fall frost near October 8 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Four Square Mile in?
Four Square Mile 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 Four Square Mile?
There are roughly 154 frost-free days in Four Square Mile (a moderate growing season), running from the average last frost around May 7 to the first fall frost near October 8.
When should I plant tomatoes in Four Square Mile?
In Four Square Mile, start tomato seeds indoors around March 12–March 26, then transplant seedlings outdoors around May 14 once the danger of frost has passed.
Never miss a window in Four Square Mile
An email when it’s time to start seeds, transplant, and sow — timed to Four Square Mile’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Greenwood Village · 7 km
- Cherry Creek · 8 km
- Denver · 9 km
- Englewood · 10 km
- Centennial · 10 km
- Aurora · 15 km
- Littleton · 15 km
- Lone Tree · 17 km
Frost dates recorded at CHERRY CREEK DAM, 8 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 Four Square Mile, CO — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00051547. Retrieved from https://blissgarden.com/colorado/four-square-mile.