Frost Dates for Thompson Falls, MT 59873
Last spring frost June 19 · First fall frost September 5 · 78 frost-free days · USDA Zone 6a
ZIP 59873 has about 2,920 people.
Short season: 78 frost-free days. Spring frost risk spans May 20–July 20 (61 days). Fall frost risk spans August 13–September 27 (45 days).
Frost probability for 59873
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | July 20 | June 19 | May 20 |
| Fall (first frost) | August 13 | September 5 | September 27 |
Dates come from NOAA 1971–2000 freeze probabilities at HAUGAN 1 W (36.1 km away); the 50% date is the median year.
Which crops fit a 78-day season in Thompson Falls
In Thompson Falls (78 frost-free days, a short season), 27 of 56 planner crops fit outright, 9 get two plantings, 5 need an indoor start, 2 need a faster variety, 12 don't reliably mature, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | May 15 | Jul 3–Jul 10 | 36 | no-fit: Needs 80 days; Thompson Falls has 36 after Jul 3. | — |
| Pepper | May 8 | Jul 3–Jul 10 | 36 | no-fit: Needs 75 days; Thompson Falls has 36 after Jul 3. | — |
| Lettuce | Apr 24 | May 22–May 29 | 113 | two-plantings: Plant May 22 and again by Jul 15; both mature before Sep 12. | Jul 15 |
| Carrots | — | May 29–Jun 5 | 120 | fits: 70 days to maturity, 120 available after May 29. | Jul 4 |
| Cucumber | May 29 | Jul 3–Jul 10 | 50 | head-start: Even planted out Jul 3, the outdoor season is about 10 days short; choose an early variety or grow under cover. | — |
| Beans | — | Jun 26–Jul 10 | 64 | fits: 60 days to maturity, 64 available after Jun 26. | — |
| Peas | — | Apr 24–Jul 3 | 141 | fits: 65 days to maturity, 141 available after Apr 24. | Jun 25 |
| Zucchini | Jun 5 | Jul 3–Jul 10 | 50 | head-start: Even planted out Jul 3, the outdoor season is about 5 days short; choose an early variety or grow under cover. | — |
| Onion | Mar 27 | May 22–Jun 5 | 113 | fits: 100 days to maturity, 113 available after May 22. | — |
| Spinach | — | Apr 24–Jun 12 | 155 | two-plantings: Plant Apr 24 and again by Aug 3; both mature before Sep 26. | Aug 3 |
| Kale | Apr 10 | May 22–Jun 5 | 127 | two-plantings: Plant May 22 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Broccoli | Apr 24 | May 22–Jun 5 | 113 | fits: 80 days to maturity, 113 available after May 22. | Jun 10 |
| Cabbage | Apr 24 | May 22–Jun 5 | 127 | fits: 70 days to maturity, 127 available after May 22. | Jul 4 |
| Radish | — | Apr 24–Jul 17 | 141 | two-plantings: Plant Apr 24 and again by Aug 4; both mature before Sep 12. | Aug 4 |
| Beets | — | Apr 24–Jul 17 | 141 | two-plantings: Plant Apr 24 and again by Jul 5; both mature before Sep 12. | Jul 5 |
| Potatoes | — | Jun 5–Jun 12 | 99 | fits: 90 days to maturity, 99 available after Jun 5. | — |
| Garlic | — | Sep 5 | 183 | overwinter: Plant Sep 5 to Sep 26; harvest the following summer. | Sep 26 |
| Strawberry | — | May 15–Jul 10 | 134 | perennial: A perennial: plant May 15; it fruits from the following year and keeps producing for several years. | — |
| Corn | May 22 | Jun 26–Jul 3 | 50 | no-fit: Needs 75 days; Thompson Falls has 50 after Jun 26. | — |
| Pumpkin | Jun 5 | Jul 3–Jul 3 | 43 | no-fit: Needs 100 days; Thompson Falls has 43 after Jul 3. | — |
| Cauliflower | May 8 | Jun 12–Jun 26 | 92 | fits: 75 days to maturity, 92 available after Jun 12. | Jun 15 |
| Swiss Chard | Apr 24 | Jun 5–Jun 5 | 99 | fits: 55 days to maturity, 99 available after Jun 5. | Jul 5 |
| Arugula | — | Apr 24–Jul 17 | 155 | two-plantings: Plant Apr 24 and again by Aug 3; both mature before Sep 26. | Aug 3 |
| Brussel Sprouts | Apr 24 | May 22–Jun 5 | 127 | fits: 100 days to maturity, 127 available after May 22. | Jun 4 |
| Butternut Squash | Jun 5 | Jul 3–Jul 10 | 43 | no-fit: Needs 100 days; Thompson Falls has 43 after Jul 3. | — |
| Eggplant | May 1 | Jul 3–Jul 10 | 36 | no-fit: Needs 70 days; Thompson Falls has 36 after Jul 3. | — |
| Okra | May 22 | Jun 26–Jul 3 | 57 | fits: 55 days to maturity, 57 available after Jun 26. | — |
| Basil | May 15 | Jul 10–Jul 10 | 43 | head-start: Even planted out Jul 10, the outdoor season is about 17 days short; choose an early variety or grow under cover. | — |
| Cilantro | — | May 22–Jun 12 | 113 | fits: 50 days to maturity, 113 available after May 22. | Jul 10 |
| Parsley | Apr 10 | Jun 26–Jul 3 | 78 | fits: 70 days to maturity, 78 available after Jun 26. | — |
| Celery | Apr 10 | Jun 26–Jul 10 | 78 | no-fit: Needs 120 days; Thompson Falls has 78 after Jun 26. | — |
| Scallions | Apr 10 | May 22–Jun 5 | 127 | fits: 60 days to maturity, 127 available after May 22. | Jul 14 |
| Turnip | — | May 22–Jun 5 | 127 | two-plantings: Plant May 22 and again by Jul 24; both mature before Sep 26. | Jul 24 |
| Kohlrabi | — | May 8–May 22 | 141 | two-plantings: Plant May 8 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Bok Choy | May 22 | Jun 12–Jun 19 | 92 | fits: 45 days to maturity, 92 available after Jun 12. | Jul 15 |
| Collards | Apr 10 | May 22–Jun 5 | 127 | fits: 60 days to maturity, 127 available after May 22. | Jul 14 |
| Cantaloupe | Jun 5 | Jul 3–Jul 10 | 36 | no-fit: Needs 85 days; Thompson Falls has 36 after Jul 3. | — |
| Chives | Mar 27 | Jun 26–Jul 3 | 92 | fits: 90 days to maturity, 92 available after Jun 26. | — |
| Dill | — | Apr 24–Jul 17 | 141 | two-plantings: Plant Apr 24 and again by Jul 5; both mature before Sep 12. | Jul 5 |
| Oregano | Apr 10 | Jun 26–Jul 3 | 92 | fits: 80 days to maturity, 92 available after Jun 26. | — |
| Rosemary | Mar 27 | Jun 26–Jul 3 | 78 | head-start: Even planted out Jun 26, the outdoor season is about 2 days short; choose an early variety or grow under cover. | — |
| Sage | Apr 24 | Jun 26–Jul 3 | 92 | fits: 75 days to maturity, 92 available after Jun 26. | — |
| Thyme | Apr 10 | Jun 26–Jul 3 | 92 | fits: 90 days to maturity, 92 available after Jun 26. | — |
| Calendula | May 8 | Jun 5–Jun 19 | 99 | fits: 50 days to maturity, 99 available after Jun 5. | Jul 10 |
| Cosmos | May 22 | Jun 19–Jul 3 | 64 | fits: 60 days to maturity, 64 available after Jun 19. | — |
| Lavender | Mar 27 | Jun 19–Jul 3 | 99 | fits: 90 days to maturity, 99 available after Jun 19. | — |
| Marigolds | May 8 | Jun 19–Jun 26 | 64 | fits: 50 days to maturity, 64 available after Jun 19. | — |
| Melons | Jun 5 | Jul 3–Jul 10 | 36 | no-fit: Needs 85 days; Thompson Falls has 36 after Jul 3. | — |
| Mint | — | Jun 19–Jul 3 | 99 | fits: 90 days to maturity, 99 available after Jun 19. | — |
| Nasturtiums | May 22 | Jun 19–Jun 26 | 64 | fits: 55 days to maturity, 64 available after Jun 19. | — |
| Pole Beans | — | Jun 26–Jul 10 | 57 | tight: Direct-sow only; pick a variety under 57 days. | — |
| Spaghetti Squash | Jun 5 | Jul 3–Jul 10 | 43 | no-fit: Needs 90 days; Thompson Falls has 43 after Jul 3. | — |
| Sunflowers | — | Jun 19–Jul 3 | 64 | tight: Direct-sow only; pick a variety under 64 days. | — |
| Tomatillos | Apr 24 | Jun 26–Jul 3 | 43 | no-fit: Needs 75 days; Thompson Falls has 43 after Jun 26. | — |
| Watermelon | Jun 5 | Jun 26–Jul 3 | 43 | no-fit: Needs 80 days; Thompson Falls has 43 after Jun 26. | — |
| Yellow Squash | Jun 5 | Jul 3–Jul 10 | 50 | head-start: Even planted out Jul 3, the outdoor season is about 5 days short; choose an early variety or grow under cover. | — |
| Zinnias | May 22 | Jun 19–Jul 3 | 64 | fits: 60 days to maturity, 64 available after Jun 19. | — |
Month by month in Thompson Falls
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start the slowest-growing crops indoors: onions, leeks, and celery (10–12 weeks before last frost). |
| March | Start indoors: Chives (Mar 27), Lavender (Mar 27), Onion (Mar 27), Rosemary (Mar 27). |
| April | Start indoors: Celery (Apr 10), Collards (Apr 10), Kale (Apr 10), Oregano (Apr 10), Parsley (Apr 10), Scallions (Apr 10), +8 more. Direct sow from: Arugula (Apr 24), Beets (Apr 24), Dill (Apr 24), Peas (Apr 24), Radish (Apr 24), Spinach (Apr 24). |
| May | Start indoors: Eggplant (May 1), Calendula (May 8), Cauliflower (May 8), Marigolds (May 8), Pepper (May 8), Basil (May 15), +8 more. Direct sow from: Kohlrabi (May 8), Cilantro (May 22), Turnip (May 22), Carrots (May 29). Transplant from: Broccoli (May 22), Brussel Sprouts (May 22), Cabbage (May 22), Collards (May 22), Kale (May 22), Lettuce (May 22), +2 more. Plant: Strawberry (May 15). |
| June | Start indoors: Butternut Squash (Jun 5), Cantaloupe (Jun 5), Melons (Jun 5), Pumpkin (Jun 5), Spaghetti Squash (Jun 5), Watermelon (Jun 5), +2 more. Direct sow from: Potatoes (Jun 5), Sunflowers (Jun 19), Beans (Jun 26), Pole Beans (Jun 26). Transplant from: Calendula (Jun 5), Swiss Chard (Jun 5), Bok Choy (Jun 12), Cauliflower (Jun 12), Cosmos (Jun 19), Lavender (Jun 19), +15 more. Last frost around June 19. Last sowing dates: Brussel Sprouts (Jun 4), Broccoli (Jun 10), Cauliflower (Jun 15), Peas (Jun 25). |
| July | Transplant from: Butternut Squash (Jul 3), Cantaloupe (Jul 3), Cucumber (Jul 3), Eggplant (Jul 3), Melons (Jul 3), Pepper (Jul 3), +6 more. Last sowing dates: Cabbage (Jul 4), Carrots (Jul 4), Beets (Jul 5), Dill (Jul 5), Swiss Chard (Jul 5), Calendula (Jul 10), +8 more. |
| August | Last sowing dates: Arugula (Aug 3), Spinach (Aug 3), Radish (Aug 4). |
| September | Direct sow from: Garlic (Sep 5). First frost around September 5. Last sowing dates: Garlic (Sep 26). |
| October | Harvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year. |
| November | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Thompson Falls, MT (ZIP 59873)?
The median last spring frost date for Thompson Falls, MT (ZIP code 59873) is around June 19. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before May 20; one in ten it runs past July 20.
What is the first fall frost date in Thompson Falls, MT?
The median first fall frost date for Thompson Falls, MT is around September 5. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around August 13 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Thompson Falls, MT?
The frost-free growing season in Thompson Falls is about 78 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Thompson Falls (78 frost-free days, a short season), 27 of 56 planner crops fit outright, 9 get two plantings, 5 need an indoor start, 2 need a faster variety, 12 don't reliably mature, 1 crop is perennial.
What USDA hardiness zone is Thompson Falls, MT?
Thompson Falls, MT is in USDA hardiness zone 6a (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Thompson Falls, MT?
Start tomatoes indoors May 15 and plant out Jul 3 in Thompson Falls. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Thompson Falls?
Two: plant May 22 and again by Jul 15; both mature before Sep 12.
When do I plant garlic in Thompson Falls?
Sep 5 to Sep 26; it overwinters and is ready the following summer.
Can I grow Celery in Thompson Falls?
Not reliably outdoors. Needs 120 days; Thompson Falls has 78 after Jun 26.
Which nearby ZIP has a longer season?
Libby (ZIP 59923) has 94 frost-free days, 16 more than Thompson Falls (ZIP 59873). See Libby ZIP 59923 frost dates
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