Great Falls, Montana planting calendar and frost dates
Great Falls is in USDA hardiness zone 4b. The last spring frost typically comes around May 19 and the first fall frost around September 24, giving about 126 frost-free days a year.
- Hardiness zone
- Zone 4b
- Typical last frost
- May 19
- Typical first frost
- September 24
- Frost-free season
- 126 days
Frost dates in Great Falls
Last spring frost
- May 7Risky: frost later than this in 9 years out of 10
- May 19Typical: a later frost in half of years
- June 2Safe: a later frost only 1 year in 10
First fall frost
- September 9Risky: frost earlier than this 1 year in 10
- September 24Typical: an earlier frost in half of years
- October 5Late: frost before this in 9 years out of 10
The growing season between the typical last and first frosts is about 126 days. Frost here means a low of 32°F at the weather station. A hard freeze (28°F), which damages most hardy crops too, typically ends around May 5 and returns around October 3.
NOAA U.S. Climate Normals 1991-2020 for Great Falls International Airport, 4.2 miles WSW of the city center and 335 feet higher. Low-lying and rural spots often frost later in spring and earlier in fall than airports and city centers.
What to plant each month in Great Falls
January
Start indoors: onions
February
Start indoors: collard greens, leeks, onions, petunias, ranunculus
March
Start indoors: black-eyed susans, broccoli, cabbages, cauliflower, chives, collard greens, ginger, kale, leeks, lettuce, marigolds, onions, oregano, parsley, petunias, ranunculus, rosemary, sage, snapdragons
April
Start indoors: black-eyed susans, cabbages, celery, chives, cilantro, collard greens, eggplants, ginger, lettuce, marigolds, nasturtiums, peppers, ranunculus, sage, snapdragons, spinach, swiss chard, tomatoes
Plant or sow outdoors: beets, black-eyed susans, blackberries, blueberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, collard greens, figs, garlic, gladioli, grapes, grass seed, hollyhocks, kale, leeks, lettuce, onions, parsley, peas, poppies, radishes, ranunculus, raspberries, rhubarb, roses, spinach, strawberries, swiss chard, turnips, wildflowers
May
Start indoors: basil, cantaloupes, cosmos, cucumbers, eggplants, okra, peppers, pumpkins, ranunculus, tomatoes, watermelons, winter squash, zucchini
Plant or sow outdoors: asparagus, beets, black-eyed susans, blackberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, dahlias, dill, figs, garden mums, ginger, gladioli, grapes, green onions, kentucky bluegrass, lavenders, leeks, lettuce, lilies, marigolds, mints, nasturtiums, onions, oregano, parsley, perennial ryegrass, petunias, potatoes, radishes, ranunculus, rosemary, roses, sage, snapdragons, spinach, sunflowers, sweet corn, sweet peas, swiss chard, tall fescue, thyme, turnips
June
Start indoors: cosmos, cucumbers, okra, pumpkins, winter squash, zinnias, zucchini
Plant or sow outdoors: asparagus, basil, cantaloupes, cucumbers, eggplants, garden mums, ginger, grapes, green beans, green onions, kentucky bluegrass, lavenders, lilies, marigolds, mints, nasturtiums, oregano, parsley, peppers, perennial ryegrass, petunias, pumpkins, rosemary, sage, st. augustinegrass, sunflowers, sweet corn, sweet peas, tall fescue, thyme, tomatoes, watermelons, winter squash, zucchini
Plant for fall: brussels sprouts, collard greens, lettuce, swiss chard
July
Start indoors: zinnias
Plant or sow outdoors: bermudagrass, cantaloupes, celery, centipedegrass, cosmos, cucumbers, eggplants, green beans, green onions, okra, peanuts, peppers, pumpkins, st. augustinegrass, sweet potatoes, tomatoes, watermelons, winter squash, zinnias, zoysiagrass, zucchini
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, carrots, cauliflower, clematis, collard greens, coneflowers, daylilies, hostas, hydrangeas, kale, lettuce, peas, radishes, roses, saffron, snapdragons, spinach, swiss chard, turnips
August
Plant or sow outdoors: bermudagrass, centipedegrass, zinnias, zoysiagrass
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, cauliflower, clematis, coneflowers, crocuses, daffodils, daylilies, grass seed, hostas, hyacinths, hydrangeas, kale, lilies, ornamental alliums, peonies, radishes, roses, saffron, spinach, tulips, turnips
September
Plant for fall: crocuses, daffodils, daylilies, garlic, hyacinths, lilies, ornamental alliums, peonies, tulips
October
Plant for fall: crocuses, garlic, hyacinths, ornamental alliums, tulips
Frost dates and zones by ZIP code in Great Falls
All 3 of Great Falls's main ZIP codes take their frost dates from Great Falls International Airport, so the dates on this page apply across the city. Every one of them is in zone 4b.
Planting dates for popular crops in Great Falls
| Plant | Start indoors | Plant or sow outdoors | Fall planting |
|---|---|---|---|
| Tomatoes | Apr 24 to May 8 | Jun 19 to Jul 3 | — |
| Strawberries | — | Apr 7 to 21 | — |
| Lettuce | Mar 24 to Apr 7 | May 12 to 26 | Jun 25 to Jul 30 |
| Cilantro | Apr 7 to 21 | May 19 to 26 | — |
| Basil | May 1 to 15 | Jun 19 to 26 | — |
| Potatoes | — | May 12 to 19 | — |
| Garlic | — | Apr 7 to 21 | Sep 24 to Oct 8 |
| Onions | Jan 27 to Mar 10 | Apr 21 to May 5 | — |
| Cucumbers | May 22 to Jun 5 | Jun 19 to Jul 3 | — |
| Pumpkins | May 22 to Jun 5 | Jun 19 to Jul 3 | — |
| Peppers | Apr 3 to May 1 | Jun 19 to Jul 3 | — |
| Carrots | — | Apr 28 to May 19 | Jul 2 to 23 |
| Sweet Potatoes | — | Jul 6 to 13 | — |
| Watermelons | May 15 to 29 | Jun 19 to Jul 3 | — |
| Sweet Corn | — | May 19 to Jun 2 | — |
| Green Beans | — | Jun 19 to Jul 3 | — |
| Zucchini | May 22 to Jun 5 | Jun 19 to Jul 3 | — |
| Broccoli | Mar 3 to 24 | Apr 21 to May 5 | Jul 9 to Aug 6 |
| Peas | — | Apr 7 to 21 | Jul 2 to 16 |
| Spinach | Apr 7 to 14 | May 12 to 26 | Jul 16 to Aug 20 |
| Sunflowers | — | May 19 to Jun 9 | — |
| Zinnias | Jun 28 to Jul 5 | Jul 26 to Aug 9 | — |
| Tulips | — | — | Aug 13 to Oct 8 |
| Daffodils | — | — | Aug 13 to Sep 24 |
| Grass Seed | — | Apr 7 to 21 | Aug 13 to 27 |
Nearby cities
- Bozeman, MT zone 5a, last frost May 23
- Missoula, MT zone 5b, last frost May 10
- Billings, MT zone 5a, last frost May 10
- Coeur d'Alene, ID zone 6b, last frost Apr 22
- Spokane Valley, WA zone 7a, last frost Apr 26
- Idaho Falls, ID zone 5b, last frost May 23
Planting in MontanaAbout zone 4bPrintable calendar for Great Falls
Questions
When is the last frost in Great Falls?
Around May 19 in a typical year, based on NOAA's 1991-2020 records for Great Falls International Airport. There is still a 1 in 10 chance of frost after June 2.
What planting zone is Great Falls in?
USDA hardiness zone 4b (2023 map). The zone tells you which perennials survive the winter; planting dates depend on frost dates instead.
When should I plant tomatoes in Great Falls?
Start seeds indoors April 24 to May 8 and set plants out June 19 to July 3.
When is the first frost in Great Falls?
Around September 24 in a typical year, and before September 9 about 1 year in 10.