When to plant in Louisville, CO
USDA Zone 6aLouisville, Colorado frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
Zone 6a means Louisville sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
Frost probability
BOULDER · 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 Louisville’s own odds, recorded at BOULDER.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 2 | May 17 | May 5 | Sep 13 | Sep 28 | Oct 10 |
| 32°F | May 18 | May 6 | Apr 24 | Sep 21 | Oct 5 | Oct 18 |
| 28°F | May 10 | Apr 27 | Apr 10 | Sep 30 | Oct 15 | Oct 30 |
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 Louisville, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 17 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.
Louisville planting FAQ
When is the last spring frost in Louisville, CO?
Louisville's average last spring frost falls near May 6 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Louisville, CO?
The first fall frost in Louisville typically arrives around October 5 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Louisville in?
Louisville 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 Louisville?
There are roughly 152 frost-free days in Louisville (a moderate growing season), running from the average last frost around May 6 to the first fall frost near October 5.
When should I plant tomatoes in Louisville?
In Louisville, start tomato seeds indoors around March 11–March 25, then transplant seedlings outdoors around May 13 once the danger of frost has passed.
Never miss a window in Louisville
An email when it’s time to start seeds, transplant, and sow — timed to Louisville’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Superior · 4 km
- Lafayette · 5 km
- Broomfield · 8 km
- Gunbarrel · 11 km
- Boulder · 11 km
- Erie · 12 km
- Westminster · 12 km
- Arvada · 15 km
Frost dates recorded at BOULDER, 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 Louisville, CO — Frost Dates & Zone 6a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00050848. Retrieved from https://blissgarden.com/colorado/louisville.