Iron Mountain, Michigan climate: Normal weather by month, frost dates and records
Iron Mountain's normal year runs from 6°F January nights to 80°F July afternoons, with 20.8 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 5.4°C, January lows of −15°C, July highs of 27°C, 527 mm of precipitation a year.
- NOAA stationIron Mountain Ford Airport
- Station IDUSW00094893
- Location45.82°N 88.11°W
- Elevation1,149 ft (350 m)
- Population7,524
On October 14, the normal high in Iron Mountain is 56°F and the normal low 35°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Iron Mountain.
- Jan 24° 6°
- Feb 27° 7°
- Mar 38° 17°
- Apr 52° 27°
- May 66° 40°
- Jun 76° 50°
- Jul 80° 54°
- Aug 78° 53°
- Sep 70° 45°
- Oct 55° 34°
- Nov 40° 24°
- Dec 29° 13°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Iron Mountain each month?
July is the warmest month, with normal highs of 80°F; January the coldest, with normal lows of 6°F. The most precipitation falls in June (2.99 in), the least in January (0.47 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 24°F | 6°F | 14.7°F | 0.47 | 6 | <1 | 31 | 9 h |
| February | 27°F | 7°F | 17.0°F | 0.51 | 5 | <1 | 28 | 10 h 20 min |
| March | 38°F | 17°F | 27.6°F | 0.87 | 6 | <1 | 28 | 11 h 50 min |
| April | 52°F | 27°F | 39.8°F | 1.59 | 9 | <1 | 22 | 13 h 30 min |
| May | 66°F | 40°F | 52.9°F | 2.20 | 11 | <1 | 7 | 14 h 50 min |
| June | 76°F | 50°F | 62.8°F | 2.99 | 12 | 1 | <1 | 15 h 40 min |
| July | 80°F | 54°F | 67.3°F | 2.74 | 11 | 3 | <1 | 15 h 20 min |
| August | 78°F | 53°F | 65.3°F | 2.44 | 11 | 1 | <1 | 14 h 10 min |
| September | 70°F | 45°F | 57.4°F | 2.94 | 12 | <1 | 2 | 12 h 40 min |
| October | 55°F | 34°F | 44.7°F | 2.20 | 10 | <1 | 15 | 11 h |
| November | 40°F | 24°F | 31.9°F | 1.15 | 7 | <1 | 25 | 9 h 30 min |
| December | 29°F | 13°F | 20.6°F | 0.65 | 6 | <1 | 30 | 8 h 40 min |
| Year (annual) | 53°F | 31°F | 41.8°F | 20.75 | 104 | 6 | 187 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −5°C | −15°C | −9.6°C | 12 mm |
| February | −3°C | −14°C | −8.3°C | 13 mm |
| March | 3°C | −8°C | −2.4°C | 22 mm |
| April | 11°C | −3°C | 4.3°C | 40 mm |
| May | 19°C | 4°C | 11.6°C | 56 mm |
| June | 24°C | 10°C | 17.1°C | 76 mm |
| July | 27°C | 12°C | 19.6°C | 70 mm |
| August | 25°C | 12°C | 18.5°C | 62 mm |
| September | 21°C | 7°C | 14.1°C | 75 mm |
| October | 13°C | 1°C | 7.1°C | 56 mm |
| November | 5°C | −5°C | −0.1°C | 29 mm |
| December | −2°C | −11°C | −6.3°C | 17 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Iron Mountain-Kingsford Wastewater Treatment Plant (3 miles away), gets 61 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094893; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Iron Mountain?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, May has the fewest days with rain (11).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094893.
When is the last frost in Iron Mountain?
In Iron Mountain, the last spring frost (32°F) comes after May 25 in half of years and after June 6 in one year in ten; the first autumn frost comes before September 24 in half of years and before September 8 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- May 251 year in 10 after June 6; 9 in 10 after May 10
- First autumn frost, half of years before
- September 241 year in 10 before September 8; 9 in 10 before October 7
NOAA puts the median frost-free season at 121 days, and the season without a hard freeze (28°F) at 145 days.
A hard freeze (28°F) comes after May 11 in half of springs and before October 5 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Iron Mountain in zone 4b in ZIP code 49802, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Iron Mountain's NOAA station is in zone 4b: the coldest night of a typical year reaches −20°F (23 complete years).
Frost dates for every NOAA station in Michigan · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00094893; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Iron Mountain?
In a normal year in Iron Mountain, 6 days a year reach 90°F, 187 nights fall to 32°F or colder and 104 days bring measurable precipitation.
- Days at 90°F or more
- 6a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 187a normal year
- Days that stay below freezing
- 81high of 32°F or less
- Days with 0.01 inch of precipitation
- 104a normal year
The highest temperature in this station's record (since 1996) is 100°F, on July 13, 2026; the lowest is −28°F, on December 25, 2004.
The wettest calendar year on that record is 2010, with 32.13 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00094893; records: ACIS (NOAA Regional Climate Centers), station USW00094893. Records use complete months only; a month missing more than three days is left out.
How sunny is Iron Mountain?
Over a year 71% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Iron Mountain, 3.7 kWh per square metre a day. July is the sunniest month (78%) and December the cloudiest (56%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 65% | 1.6 |
| February | 73% | 2.6 |
| March | 73% | 3.8 |
| April | 68% | 4.6 |
| May | 69% | 5.4 |
| June | 72% | 6.0 |
| July | 78% | 6.1 |
| August | 76% | 5.1 |
| September | 73% | 3.9 |
| October | 65% | 2.5 |
| November | 61% | 1.5 |
| December | 56% | 1.1 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Iron Mountain need?
A normal year in Iron Mountain brings 8,708 heating degree days, 62% more than the median U.S. place (5,373), and 296 cooling degree days, 67% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,882 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,561 | 0 |
| February | 1,344 | 0 |
| March | 1,161 | 0 |
| April | 758 | 0 |
| May | 388 | 13 |
| June | 121 | 56 |
| July | 50 | 119 |
| August | 71 | 80 |
| September | 255 | 25 |
| October | 631 | 2 |
| November | 993 | 0 |
| December | 1,376 | 0 |
| Year (annual) | 8,708 | 296 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094893. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Iron Mountain been warmer than normal lately?
2025 averaged 43.0°F, 1.2°F above the 1991-2020 normal of 41.8°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 44.1°F | +2.3°F | 12.65 |
| 2022 | 41.6°F | −0.2°F | 14.73 |
| 2023 | 44.4°F | +2.6°F | 12.04 |
| 2024 | 45.9°F | +4.1°F | 14.82 |
| 2025 | 43.0°F | +1.2°F | – |
Source: observed years: ACIS, station USW00094893. A year counts only with all twelve months complete.
How does Iron Mountain's climate compare?
Iron Mountain is warmer than 11 of the other 139 places with their own NOAA record in Michigan, and wetter than 0. Across the 7,247 U.S. stations with normals, its annual mean of 41.8°F is warmer than 9%.
In the Köppen classification computed from these normals, Iron Mountain is Dfb: continental, no dry season, warm summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Iron Mountain share this climate record?
Kingsford has no NOAA station with 1991-2020 normals of its own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Kingsford, MI5,125 people · 1 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Iron Mountain's climate
What is the coldest month in Iron Mountain?
January, with a normal high of 24°F and a normal low of 6°F. The warmest is July (80°F by day, 54°F at night).
Does it snow in Iron Mountain?
Yes. NOAA publishes no 1991-2020 snowfall normal for Iron Mountain's NOAA station; the nearest record that keeps one, Iron Mountain-Kingsford Wastewater Treatment Plant (3 miles away), records 61 inches of snow in a normal year.
What is the rainiest month in Iron Mountain?
June, with 2.99 in of precipitation in a normal year; the driest is January with 0.47 in.
What plant hardiness zone is Iron Mountain in?
The USDA's 2023 map puts Iron Mountain in zone 4b in ZIP code 49802, the nearest ZIP area. By the same method at Iron Mountain's NOAA station, the coldest night of a typical year reaches −20°F (23 years, 1991-2020): zone 4b.
How late can frost come in Iron Mountain?
In half of years the last 32°F night comes after May 25; in one year in ten it comes after June 6. Waiting until June 6 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Michigan climateThe statewide normals and every place in the state
- Iron Mountain-Kingsford Wastewater Treatment Plant, MI2 miles from this station, 42.5°F a year
- Florence, WI11 miles from this station, 40.4°F a year
- Goodman, WI18 miles from this station, 41.3°F a year
- Stambaugh (2 mi SSE), MI30 miles from this station, 38.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made