USDA hardiness zone lookup
Fort Collins (South) (80525) — USDA Zone 5b
Fort Collins (South), Colorado · 139-day growing season
Frost dates and growing season for 80525
| USDA hardiness zone | Zone 5b |
|---|---|
| Average last spring frost | May 12 |
| Average first fall frost | September 28 |
| Growing season length | ~139 days |
| Temperature range (F) | -20 to -10°F |
| Temperature range (C) | -29 to -23°C |
These are 50%-probability averages modeled from this ZIP'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 12, but in a colder-than-average year it 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 Fort Collins (South)
Fort Collins (South), Colorado sits in USDA Zone 5b, with roughly 139 frost-free days between an average last spring frost around May 12 and a first fall frost around September 28. 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 Fort Collins (South)
Fort Collins (South) falls in USDA Zone 5b, which means the same hardiness constraints apply as the full Zone 5 guide. Vegetables, herbs, and fruit trees rated to Zone 5b (or hardier) will overwinter here in a typical year.
- Tomatoes (full range of varieties)
- Peppers
- Eggplant
- Squash, melons, cucumbers
- Beans (bush + pole)
- Sweet corn
- Apples, pears, plums
- Cherries (sweet + sour)
- Blueberries, raspberries
- Garlic
What to plant in Fort Collins (South) this week
Fort Collins (South)'s last frost is around May 12. 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 5
- When to plant peppers in zone 5
- When to plant basil in zone 5
- When to plant bush beans in zone 5
- When to plant cucumbers in zone 5
Full planting calendar for Fort Collins (South)
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 5 averages:
- When to plant tomatoes in zone 5
- When to plant peppers in zone 5
- When to plant basil in zone 5
- When to plant garlic in zone 5
- When to plant lettuce in zone 5
- When to plant bush beans in zone 5
- When to plant cucumbers in zone 5
- When to plant summer squash in zone 5
- When to plant peas in zone 5
- When to plant carrots in zone 5
Local microclimate notes
Zone tables give you the average — but Fort Collins (South)gardens 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) is more accurate than 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 this ZIP's USDA hardiness zone and regional NOAA 1991-2020 climate normals — they are zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations are drawn from US Cooperative Extension references and curated by the Growli editorial team. Last reviewed May 2026.
Nearby ZIP codes in Colorado
- 80202 — Denver (Zone 6a)
- 80302 — Boulder (Zone 6a)
- 80903 — Colorado Springs (Zone 6a)
- 81501 — Grand Junction (Zone 7a)
- 80521 — Fort Collins (Zone 5b)
- 80211 — Denver (Highlands) (Zone 6a)
- 80218 — Denver (Capitol Hill) (Zone 6a)
- 80220 — Denver (East) (Zone 6a)
- 80239 — Denver (Montbello) (Zone 6a)
- 80012 — Aurora (Central) (Zone 6a)
- 80013 — Aurora (Southeast) (Zone 6a)
- 80015 — Aurora (Smoky Hill) (Zone 5b)
- Browse all US ZIP codes by state