USDA hardiness zone lookup
Westminster, CO — USDA Zone 6a
Westminster, Colorado · 150-day growing season
Frost dates and growing season in Westminster
| USDA hardiness zone | Zone 6a |
|---|---|
| Average last spring frost | May 6 |
| Average first fall frost | October 3 |
| Growing season length | ~150 days |
| Temperature range (F) | -10 to 0°F |
| Temperature range (C) | -23 to -18°C |
All of Westminster's mapped ZIP codes fall in the same hardiness band, Zone 6a.
These are 50%-probability averages modeled from Westminster's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by May 6, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.
Growing season in Westminster
Westminster, Colorado sits in USDA Zone 6a, with roughly 150 frost-free days between an average last spring frost around May 6 and a first fall frost around October 3. That is a standard temperate season — most common vegetables finish comfortably, and a single main planting plus one succession round works well.
What grows in Westminster
Westminster falls in USDA Zone 6a, so the same hardiness constraints apply as the full Zone 6 guide. Vegetables, herbs, and fruit trees rated to Zone 6a (or hardier) will overwinter here in a typical year.
- Tomatoes (all types)
- Peppers, eggplant
- Squash, melons, cucumbers
- Beans, peas
- Sweet corn
- Apples, pears, peaches, plums
- Cherries, blueberries
- Asparagus, rhubarb
- Garlic (fall-planted)
- Strawberries
What to plant in Westminster this week
Westminster's last frost is around May 6. This is the spring transplant window — start tomatoes and peppers indoors if you haven't, and direct-sow cold-tolerant crops now.
- When to plant tomatoes in zone 6
- When to plant peppers in zone 6
- When to plant basil in zone 6
- When to plant bush beans in zone 6
- When to plant cucumbers in zone 6
Full planting calendar for Westminster
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 6 averages:
- When to plant tomatoes in zone 6
- When to plant peppers in zone 6
- When to plant basil in zone 6
- When to plant garlic in zone 6
- When to plant lettuce in zone 6
- When to plant bush beans in zone 6
- When to plant cucumbers in zone 6
- When to plant summer squash in zone 6
- When to plant peas in zone 6
- When to plant carrots in zone 6
ZIP codes in Westminster
Drill down to the precise frost window and planting calendar for a specific ZIP in Westminster:
Local microclimate notes
Zone tables give you the average — but Westminstergardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.
Source and methodology
Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Westminster's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.
Other cities in Colorado
- Arvada, CO — USDA Zone 6a
- Aurora, CO — USDA Zone 6a
- Boulder, CO — USDA Zone 6a
- Colorado Springs, CO — USDA Zone 6a
- Denver, CO — USDA Zone 6a
- Fort Collins, CO — USDA Zone 5b
- Glenwood Springs, CO — USDA Zone 6a
- Grand Junction, CO — USDA Zone 7a
- Greeley, CO — USDA Zone 5b
- Highlands Ranch, CO — USDA Zone 5b
- Lakewood, CO — USDA Zone 6a
- Littleton, CO — USDA Zone 6a
- All of Colorado by zone