USDA Hardiness Zone 4a
Frost Dates for 49935 — Iron River, Michigan
Averages from Stambaugh 2sse, Mi US, the nearest reporting station, 5 miles away.
Plant tender crops after June 4, and expect the first autumn freeze around September 10. That leaves about 95 frost-free days.
- Last spring frost
- June 4
- First fall frost
- September 10
- Growing season
- 95 days
- Hardiness zone
- 4a
50% probability
50% probability
frost-free
-30 to -25°F annual low
Planting calendar for 49935
| When | What to do |
|---|---|
| March 26 – April 9 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| April 9 – April 23 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| May 7 – May 21 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| June 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by June 18 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by August 27 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| September 10 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after June 4 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Iron River, Michigan are past their last freeze. Harvest before September 10, which leaves roughly 95 frost-free days.
ZIP 49935 sits in USDA hardiness zone 4a, meaning the average coldest night of the year falls between -30 to -25°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.