When to plant in Highlands Ranch, CO
USDA Zone 6aEverything below — frost dates, hardiness zone, and what to plant when in Highlands Ranch, Colorado — is derived from the closest NOAA station with complete climate normals.
In zone 6a, Highlands Ranch gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
DENVER CENTENNIAL 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 Highlands Ranch’s own odds, recorded at DENVER CENTENNIAL AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 30 | May 15 | May 3 | Sep 17 | Oct 1 | Oct 12 |
| 32°F | May 17 | May 5 | Apr 24 | Sep 25 | Oct 8 | Oct 20 |
| 28°F | May 9 | Apr 25 | Apr 10 | Oct 4 | Oct 17 | Oct 28 |
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 Highlands Ranch, 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.
Highlands Ranch planting FAQ
When is the last spring frost in Highlands Ranch, CO?
Plan for the last spring frost in Highlands Ranch around May 5 (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 Highlands Ranch, CO?
Expect Highlands Ranch'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 Highlands Ranch in?
Highlands Ranch 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 Highlands Ranch?
Highlands Ranch has about 156 frost-free days — a moderate growing season — between the average last spring frost (May 5) and first fall frost (October 8).
When should I plant tomatoes in Highlands Ranch?
For Highlands Ranch, sow tomatoes indoors about March 10–March 24 and move the seedlings out around May 12, after the last spring frost.
Never miss a window in Highlands Ranch
An email when it’s time to start seeds, transplant, and sow — timed to Highlands Ranch’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Littleton · 7 km
- Lone Tree · 9 km
- Greenwood Village · 10 km
- Columbine · 10 km
- Centennial · 11 km
- Cherry Creek · 12 km
- Englewood · 12 km
- Castle Pines · 12 km
Frost dates recorded at DENVER CENTENNIAL AP, 11 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 Highlands Ranch, CO — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00093067. Retrieved from https://blissgarden.com/colorado/highlands-ranch.