When to plant in Johnstown, CO
USDA Zone 5bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Johnstown, Colorado — all computed from Johnstown's nearest NOAA weather station.
Johnstown's nearest full-normals station sits about 20 km out, so treat these as a close estimate — local microclimate can nudge your first and last frost. In zone 5b, Johnstown gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
LOVELAND 2N · 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 Johnstown’s own odds, recorded at LOVELAND 2N.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 4 | May 22 | May 11 | Sep 8 | Sep 22 | Oct 4 |
| 32°F | May 22 | May 10 | Apr 30 | Sep 15 | Oct 1 | Oct 13 |
| 28°F | May 14 | May 2 | Apr 17 | Sep 22 | Oct 10 | Oct 22 |
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 Johnstown, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 21 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.
Johnstown planting FAQ
When is the last spring frost in Johnstown, CO?
Johnstown's average last spring frost falls near May 10 — 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 Johnstown, CO?
In Johnstown, the first 32°F freeze of fall lands around October 1 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Johnstown in?
Johnstown is in USDA hardiness zone 5b. In zone 5b, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Johnstown?
Johnstown has about 144 frost-free days — a short growing season — between the average last spring frost (May 10) and first fall frost (October 1).
When should I plant tomatoes in Johnstown?
For Johnstown, sow tomatoes indoors about March 15–March 29 and move the seedlings out around May 17, after the last spring frost.
Never miss a window in Johnstown
An email when it’s time to start seeds, transplant, and sow — timed to Johnstown’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at LOVELAND 2N, 20 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 Johnstown, CO — Frost Dates & Zone 5b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00055236. Retrieved from https://blissgarden.com/colorado/johnstown.