Frost Dates for Iron Mountain, MI 49801
Last spring frost May 27 · First fall frost September 20 · 116 frost-free days · USDA Zone 4b
ZIP 49801 has about 11,900 people.
Short season: 116 frost-free days. Spring frost risk spans May 12–June 10 (29 days). Fall frost risk spans September 9–October 2 (23 days).
Frost probability for 49801
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | June 10 | May 27 | May 12 |
| Fall (first frost) | September 9 | September 20 | October 2 |
Dates come from NOAA 1971–2000 freeze probabilities at IRON MTN-KINGSFORD WWTP (15.7 km away); the 50% date is the median year.
Which crops fit a 116-day season in Iron Mountain
In Iron Mountain (116 frost-free days, a short season), 32 of 56 planner crops fit outright, 15 get two plantings, 8 need an indoor start, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Apr 22 | Jun 10–Jun 17 | 74 | head-start: Even planted out Jun 10, the outdoor season is about 6 days short; choose an early variety or grow under cover. | — |
| Pepper | Apr 15 | Jun 10–Jun 17 | 74 | head-start: Even planted out Jun 10, the outdoor season is about 1 days short; choose an early variety or grow under cover. | — |
| Lettuce | Apr 1 | Apr 29–May 6 | 151 | two-plantings: Plant Apr 29 and again by Jul 30; both mature before Sep 27. | Jul 30 |
| Carrots | — | May 6–May 13 | 158 | fits: 70 days to maturity, 158 available after May 6. | Jul 19 |
| Cucumber | May 6 | Jun 10–Jun 17 | 88 | fits: 60 days to maturity, 88 available after Jun 10. | Jun 24 |
| Beans | — | Jun 3–Jun 17 | 102 | fits: 60 days to maturity, 102 available after Jun 3. | Jul 1 |
| Peas | — | Apr 1–Jun 10 | 179 | fits: 65 days to maturity, 179 available after Apr 1. | Jul 10 |
| Zucchini | May 13 | Jun 10–Jun 17 | 88 | fits: 55 days to maturity, 88 available after Jun 10. | Jun 29 |
| Onion | Mar 4 | Apr 29–May 13 | 151 | fits: 100 days to maturity, 151 available after Apr 29. | — |
| Spinach | — | Apr 1–May 20 | 193 | two-plantings: Plant Apr 1 and again by Aug 18; both mature before Oct 11. | Aug 18 |
| Kale | Mar 18 | Apr 29–May 13 | 165 | two-plantings: Plant Apr 29 and again by Aug 3; both mature before Oct 11. | Aug 3 |
| Broccoli | Apr 1 | Apr 29–May 13 | 151 | fits: 80 days to maturity, 151 available after Apr 29. | Jun 25 |
| Cabbage | Apr 1 | Apr 29–May 13 | 165 | fits: 70 days to maturity, 165 available after Apr 29. | Jul 19 |
| Radish | — | Apr 1–Jun 24 | 179 | two-plantings: Plant Apr 1 and again by Aug 19; both mature before Sep 27. | Aug 19 |
| Beets | — | Apr 1–Jun 24 | 179 | two-plantings: Plant Apr 1 and again by Jul 20; both mature before Sep 27. | Jul 20 |
| Potatoes | — | May 13–May 20 | 137 | fits: 90 days to maturity, 137 available after May 13. | — |
| Garlic | — | Sep 20 | 221 | overwinter: Plant Sep 20 to Oct 11; harvest the following summer. | Oct 11 |
| Strawberry | — | Apr 22–Jun 17 | 172 | perennial: A perennial: plant Apr 22; it fruits from the following year and keeps producing for several years. | — |
| Corn | Apr 29 | Jun 3–Jun 10 | 88 | fits: 75 days to maturity, 88 available after Jun 3. | — |
| Pumpkin | May 13 | Jun 10–Jun 10 | 81 | head-start: Even planted out Jun 10, the outdoor season is about 19 days short; choose an early variety or grow under cover. | — |
| Cauliflower | Apr 15 | May 20–Jun 3 | 130 | fits: 75 days to maturity, 130 available after May 20. | Jun 30 |
| Swiss Chard | Apr 1 | May 13–May 13 | 137 | two-plantings: Plant May 13 and again by Jul 20; both mature before Sep 27. | Jul 20 |
| Arugula | — | Apr 1–Jun 24 | 193 | two-plantings: Plant Apr 1 and again by Aug 18; both mature before Oct 11. | Aug 18 |
| Brussel Sprouts | Apr 1 | Apr 29–May 13 | 165 | fits: 100 days to maturity, 165 available after Apr 29. | Jun 19 |
| Butternut Squash | May 13 | Jun 10–Jun 17 | 81 | head-start: Even planted out Jun 10, the outdoor season is about 19 days short; choose an early variety or grow under cover. | — |
| Eggplant | Apr 8 | Jun 10–Jun 17 | 74 | fits: 70 days to maturity, 74 available after Jun 10. | — |
| Okra | Apr 29 | Jun 3–Jun 10 | 95 | fits: 55 days to maturity, 95 available after Jun 3. | Jun 29 |
| Basil | Apr 22 | Jun 17–Jun 17 | 81 | fits: 60 days to maturity, 81 available after Jun 17. | Jun 24 |
| Cilantro | — | Apr 29–May 20 | 151 | two-plantings: Plant Apr 29 and again by Jul 25; both mature before Sep 27. | Jul 25 |
| Parsley | Mar 18 | Jun 3–Jun 10 | 116 | fits: 70 days to maturity, 116 available after Jun 3. | Jul 5 |
| Celery | Mar 18 | Jun 3–Jun 17 | 116 | head-start: Even planted out Jun 3, the outdoor season is about 4 days short; choose an early variety or grow under cover. | — |
| Scallions | Mar 18 | Apr 29–May 13 | 165 | two-plantings: Plant Apr 29 and again by Jul 29; both mature before Oct 11. | Jul 29 |
| Turnip | — | Apr 29–May 13 | 165 | two-plantings: Plant Apr 29 and again by Aug 8; both mature before Oct 11. | Aug 8 |
| Kohlrabi | — | Apr 15–Apr 29 | 179 | two-plantings: Plant Apr 15 and again by Aug 3; both mature before Oct 11. | Aug 3 |
| Bok Choy | Apr 29 | May 20–May 27 | 130 | two-plantings: Plant May 20 and again by Jul 30; both mature before Sep 27. | Jul 30 |
| Collards | Mar 18 | Apr 29–May 13 | 165 | two-plantings: Plant Apr 29 and again by Jul 29; both mature before Oct 11. | Jul 29 |
| Cantaloupe | May 13 | Jun 10–Jun 17 | 74 | head-start: Even planted out Jun 10, the outdoor season is about 11 days short; choose an early variety or grow under cover. | — |
| Chives | Mar 4 | Jun 3–Jun 10 | 130 | fits: 90 days to maturity, 130 available after Jun 3. | — |
| Dill | — | Apr 1–Jun 24 | 179 | two-plantings: Plant Apr 1 and again by Jul 20; both mature before Sep 27. | Jul 20 |
| Oregano | Mar 18 | Jun 3–Jun 10 | 130 | fits: 80 days to maturity, 130 available after Jun 3. | — |
| Rosemary | Mar 4 | Jun 3–Jun 10 | 116 | fits: 80 days to maturity, 116 available after Jun 3. | — |
| Sage | Apr 1 | Jun 3–Jun 10 | 130 | fits: 75 days to maturity, 130 available after Jun 3. | — |
| Thyme | Mar 18 | Jun 3–Jun 10 | 130 | fits: 90 days to maturity, 130 available after Jun 3. | — |
| Calendula | Apr 15 | May 13–May 27 | 137 | two-plantings: Plant May 13 and again by Jul 25; both mature before Sep 27. | Jul 25 |
| Cosmos | Apr 29 | May 27–Jun 10 | 102 | fits: 60 days to maturity, 102 available after May 27. | Jun 24 |
| Lavender | Mar 4 | May 27–Jun 10 | 137 | fits: 90 days to maturity, 137 available after May 27. | — |
| Marigolds | Apr 15 | May 27–Jun 3 | 102 | fits: 50 days to maturity, 102 available after May 27. | Jul 4 |
| Melons | May 13 | Jun 10–Jun 17 | 74 | head-start: Even planted out Jun 10, the outdoor season is about 11 days short; choose an early variety or grow under cover. | — |
| Mint | — | May 27–Jun 10 | 137 | fits: 90 days to maturity, 137 available after May 27. | — |
| Nasturtiums | Apr 29 | May 27–Jun 3 | 102 | fits: 55 days to maturity, 102 available after May 27. | Jun 29 |
| Pole Beans | — | Jun 3–Jun 17 | 95 | fits: 65 days to maturity, 95 available after Jun 3. | Jun 19 |
| Spaghetti Squash | May 13 | Jun 10–Jun 17 | 81 | head-start: Even planted out Jun 10, the outdoor season is about 9 days short; choose an early variety or grow under cover. | — |
| Sunflowers | — | May 27–Jun 10 | 102 | fits: 70 days to maturity, 102 available after May 27. | Jun 14 |
| Tomatillos | Apr 1 | Jun 3–Jun 10 | 81 | fits: 75 days to maturity, 81 available after Jun 3. | — |
| Watermelon | May 13 | Jun 3–Jun 10 | 81 | fits: 80 days to maturity, 81 available after Jun 3. | — |
| Yellow Squash | May 13 | Jun 10–Jun 17 | 88 | fits: 55 days to maturity, 88 available after Jun 10. | Jun 29 |
| Zinnias | Apr 29 | May 27–Jun 10 | 102 | fits: 60 days to maturity, 102 available after May 27. | Jun 24 |
Month by month in Iron Mountain
| 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 4), Lavender (Mar 4), Onion (Mar 4), Rosemary (Mar 4), Celery (Mar 18), Collards (Mar 18), +5 more. |
| April | Start indoors: Broccoli (Apr 1), Brussel Sprouts (Apr 1), Cabbage (Apr 1), Lettuce (Apr 1), Sage (Apr 1), Swiss Chard (Apr 1), +14 more. Direct sow from: Arugula (Apr 1), Beets (Apr 1), Dill (Apr 1), Peas (Apr 1), Radish (Apr 1), Spinach (Apr 1), +3 more. Transplant from: Broccoli (Apr 29), Brussel Sprouts (Apr 29), Cabbage (Apr 29), Collards (Apr 29), Kale (Apr 29), Lettuce (Apr 29), +2 more. Plant: Strawberry (Apr 22). |
| May | Start indoors: Cucumber (May 6), Butternut Squash (May 13), Cantaloupe (May 13), Melons (May 13), Pumpkin (May 13), Spaghetti Squash (May 13), +3 more. Direct sow from: Carrots (May 6), Potatoes (May 13), Sunflowers (May 27). Transplant from: Calendula (May 13), Swiss Chard (May 13), Bok Choy (May 20), Cauliflower (May 20), Cosmos (May 27), Lavender (May 27), +4 more. Last frost around May 27. |
| June | Direct sow from: Beans (Jun 3), Pole Beans (Jun 3). Transplant from: Celery (Jun 3), Chives (Jun 3), Corn (Jun 3), Okra (Jun 3), Oregano (Jun 3), Parsley (Jun 3), +17 more. Last sowing dates: Sunflowers (Jun 14), Brussel Sprouts (Jun 19), Pole Beans (Jun 19), Basil (Jun 24), Cosmos (Jun 24), Cucumber (Jun 24), +7 more. |
| July | Last sowing dates: Beans (Jul 1), Marigolds (Jul 4), Parsley (Jul 5), Peas (Jul 10), Cabbage (Jul 19), Carrots (Jul 19), +9 more. |
| August | Last sowing dates: Kale (Aug 3), Kohlrabi (Aug 3), Turnip (Aug 8), Arugula (Aug 18), Spinach (Aug 18), Radish (Aug 19). |
| September | Direct sow from: Garlic (Sep 20). First frost around September 20. |
| October | Last sowing dates: Garlic (Oct 11). |
| 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 Iron Mountain, MI (ZIP 49801)?
The median last spring frost date for Iron Mountain, MI (ZIP code 49801) is around May 27. 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 12; one in ten it runs past June 10.
What is the first fall frost date in Iron Mountain, MI?
The median first fall frost date for Iron Mountain, MI is around September 20. 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 September 9 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Iron Mountain, MI?
The frost-free growing season in Iron Mountain is about 116 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 Iron Mountain (116 frost-free days, a short season), 32 of 56 planner crops fit outright, 15 get two plantings, 8 need an indoor start, 1 crop is perennial.
What USDA hardiness zone is Iron Mountain, MI?
Iron Mountain, MI is in USDA hardiness zone 4b (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 Iron Mountain, MI?
Start tomatoes indoors Apr 22 and plant out Jun 10 in Iron Mountain. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Iron Mountain?
Two: plant Apr 29 and again by Jul 30; both mature before Sep 27.
When do I plant garlic in Iron Mountain?
Sep 20 to Oct 11; it overwinters and is ready the following summer.
Can I grow Celery in Iron Mountain?
Yes, with help. Even planted out Jun 3, the outdoor season is about 4 days short; choose an early variety or grow under cover.
Which nearby ZIP has a longer season?
Escanaba (ZIP 49829) has 141 frost-free days, 25 more than Iron Mountain (ZIP 49801). See Escanaba ZIP 49829 frost dates
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