USDA hardiness zone lookup
Great Falls, MT — USDA Zone 4b
Great Falls, Montana · 125-day growing season
Frost dates and growing season in Great Falls
| USDA hardiness zone | Zone 4b |
|---|---|
| Average last spring frost | May 18 |
| Average first fall frost | September 20 |
| Growing season length | ~125 days |
| Temperature range (F) | -30 to -20°F |
| Temperature range (C) | -34 to -29°C |
All of Great Falls's mapped ZIP codes fall in the same hardiness band, Zone 4b.
These are 50%-probability averages modeled from Great Falls'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 18, 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 Great Falls
Great Falls, Montana sits in USDA Zone 4b, with roughly 125 frost-free days between an average last spring frost around May 18 and a first fall frost around September 20. 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 Great Falls
Great Falls falls in USDA Zone 4b, so the same hardiness constraints apply as the full Zone 4 guide. Vegetables, herbs, and fruit trees rated to Zone 4b (or hardier) will overwinter here in a typical year.
- Apple, pear, plum, sour cherry
- Blueberries (highbush)
- Raspberries
- Strawberries
- Tomatoes
- Peppers (short-season)
- Cucumbers
- Beans
- Squash (summer + winter)
- Garlic
What to plant in Great Falls this week
Great Falls's last frost is around May 18. 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 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
Full planting calendar for Great Falls
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 4 averages:
- When to plant tomatoes in zone 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant garlic in zone 4
- When to plant lettuce in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
- When to plant summer squash in zone 4
- When to plant peas in zone 4
- When to plant carrots in zone 4
ZIP codes in Great Falls
Drill down to the precise frost window and planting calendar for a specific ZIP in Great Falls:
Local microclimate notes
Zone tables give you the average — but Great Fallsgardens 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 Great Falls'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 Montana
- Billings, MT — USDA Zone 5a
- Bozeman, MT — USDA Zone 4b
- Butte, MT — USDA Zone 4a
- Helena, MT — USDA Zone 5a
- Kalispell, MT — USDA Zone 5a
- Livingston, MT — USDA Zone 4b
- Missoula, MT — USDA Zone 5b
- All of Montana by zone