When to plant in Westminster, CO
USDA Zone 6aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Westminster, Colorado — all computed from Westminster's nearest NOAA weather station.
Zone 6a means Westminster sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
NORTHGLENN · 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 Westminster’s own odds, recorded at NORTHGLENN.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 26 | May 12 | Apr 30 | Sep 18 | Oct 1 | Oct 14 |
| 32°F | May 14 | May 2 | Apr 18 | Sep 26 | Oct 11 | Oct 24 |
| 28°F | May 5 | Apr 20 | Apr 4 | Oct 7 | Oct 21 | Nov 4 |
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 Westminster, 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.
Westminster planting FAQ
When is the last spring frost in Westminster, CO?
Plan for the last spring frost in Westminster around May 2 (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 Westminster, CO?
In Westminster, the first 32°F freeze of fall lands around October 11 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Westminster in?
Westminster 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 Westminster?
There are roughly 162 frost-free days in Westminster (a moderate growing season), running from the average last frost around May 2 to the first fall frost near October 11.
When should I plant tomatoes in Westminster?
In Westminster, start tomato seeds indoors around March 7–March 21, then transplant seedlings outdoors around May 9 once the danger of frost has passed.
Never miss a window in Westminster
An email when it’s time to start seeds, transplant, and sow — timed to Westminster’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Federal Heights · 4 km
- Sherrelwood · 7 km
- Northglenn · 8 km
- Broomfield · 8 km
- Berkley · 9 km
- Arvada · 9 km
- Welby · 9 km
- Superior · 10 km
Frost dates recorded at NORTHGLENN, 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 Westminster, CO — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00055984. Retrieved from https://blissgarden.com/colorado/westminster.