Ironwood, Michigan climate: Normal weather by month, frost dates and records
Ironwood's normal year runs from 2°F January nights to 77°F July afternoons. (NOAA 1991-2020 normals)
In metric: a yearly mean of 4.6°C, January lows of −17°C, July highs of 25°C.
- NOAA stationIronwood #2
- Station IDUSC00204105
- Location46.47°N 90.14°W
- Elevation1,520 ft (463 m)
- Population4,938
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Ironwood.
- Jan 20° 2°
- Feb 26° 4°
- Mar 37° 14°
- Apr 49° 27°
- May 64° 40°
- Jun 73° 50°
- Jul 77° 55°
- Aug 76° 52°
- Sep 68° 46°
- Oct 53° 34°
- Nov 38° 23°
- Dec 26° 11°
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 Ironwood each month?
July is the warmest month, with normal highs of 77°F; January the coldest, with normal lows of 2°F.
| Month | High | Low | Mean | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|
| January | 20°F | 2°F | 11.2°F | – | <1 | 31 | 9 h |
| February | 26°F | 4°F | 15.1°F | – | <1 | 28 | 10 h 20 min |
| March | 37°F | 14°F | 25.5°F | – | <1 | 30 | 11 h 50 min |
| April | 49°F | 27°F | 38.1°F | – | <1 | 24 | 13 h 30 min |
| May | 64°F | 40°F | 51.9°F | – | <1 | 12 | 15 h |
| June | 73°F | 50°F | 61.6°F | – | 1 | 1 | 15 h 50 min |
| July | 77°F | 55°F | 66.0°F | – | 1 | <1 | 15 h 30 min |
| August | 76°F | 52°F | 63.9°F | – | <1 | <1 | 14 h 10 min |
| September | 68°F | 46°F | 56.6°F | – | <1 | 2 | 12 h 40 min |
| October | 53°F | 34°F | 43.7°F | – | <1 | 18 | 11 h |
| November | 38°F | 23°F | 30.3°F | – | <1 | 28 | 9 h 30 min |
| December | 26°F | 11°F | 18.6°F | – | <1 | 31 | 8 h 40 min |
| Year (annual) | 51°F | 30°F | 40.2°F | – | 1 | 203 |
The same normals in °C and millimetres
| Month | High | Low | Mean |
|---|---|---|---|
| January | −6°C | −17°C | −11.6°C |
| February | −3°C | −15°C | −9.4°C |
| March | 3°C | −10°C | −3.6°C |
| April | 10°C | −3°C | 3.4°C |
| May | 18°C | 5°C | 11.1°C |
| June | 23°C | 10°C | 16.4°C |
| July | 25°C | 13°C | 18.9°C |
| August | 24°C | 11°C | 17.7°C |
| September | 20°C | 8°C | 13.7°C |
| October | 12°C | 1°C | 6.5°C |
| November | 3°C | −5°C | −0.9°C |
| December | −3°C | −12°C | −7.4°C |
NOAA publishes no 1991-2020 snowfall normal for this station. Ironwood's own co-op station Ironwood station does: 186 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USC00204105; 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 Ironwood?
Normal highs sit between 65°F and 85°F in June, July, August and September.
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 USC00204105.
When is the last frost in Ironwood?
In Ironwood, the last spring frost (32°F) comes after May 19 in half of years and after June 3 in one year in ten; the first autumn frost comes before September 28 in half of years and before September 12 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 191 year in 10 after June 3; 9 in 10 after May 2
- First autumn frost, half of years before
- September 281 year in 10 before September 12; 9 in 10 before October 10
NOAA puts the median frost-free season at 130 days, and the season without a hard freeze (28°F) at 154 days.
A hard freeze (28°F) comes after May 5 in half of springs and before October 9 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Ironwood in zone 4b in ZIP code 54525, the nearest ZIP area.
Frost dates for every NOAA station in Michigan · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00204105; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Ironwood?
In a normal year in Ironwood, 1 day a year reaches 90°F and 203 nights fall to 32°F or colder.
- Days at 90°F or more
- 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 203a normal year
- Days that stay below freezing
- 101high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00204105.
How sunny is Ironwood?
Over a year 69% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Ironwood, 3.6 kWh per square metre a day. July is the sunniest month (78%) and December the cloudiest (52%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 59% | 1.3 |
| February | 66% | 2.3 |
| March | 68% | 3.5 |
| April | 67% | 4.5 |
| May | 68% | 5.3 |
| June | 72% | 5.9 |
| July | 78% | 6.2 |
| August | 76% | 5.1 |
| September | 72% | 3.8 |
| October | 63% | 2.4 |
| November | 58% | 1.4 |
| December | 52% | 1.0 |
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 Ironwood need?
A normal year in Ironwood brings 9,136 heating degree days, 70% more than the median U.S. place (5,373), and 126 cooling degree days, 86% 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 1,640 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,668 | 0 |
| February | 1,398 | 0 |
| March | 1,226 | 0 |
| April | 808 | 0 |
| May | 408 | 2 |
| June | 120 | 16 |
| July | 29 | 60 |
| August | 78 | 42 |
| September | 259 | 7 |
| October | 660 | 0 |
| November | 1,043 | 0 |
| December | 1,438 | 0 |
| Year (annual) | 9,136 | 126 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00204105. 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 Ironwood been warmer than normal lately?
2025 averaged 40.8°F, 0.6°F above the 1991-2020 normal of 40.2°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal |
|---|---|---|
| 2021 | 42.1°F | +1.9°F |
| 2022 | 38.8°F | −1.4°F |
| 2025 | 40.8°F | +0.6°F |
Source: observed years: ACIS, station USC00204105. A year counts only with all twelve months complete.
How does Ironwood's climate compare?
Ironwood is warmer than 3 of the other 139 places with their own NOAA record in Michigan. Across the 7,247 U.S. stations with normals, its annual mean of 40.2°F is warmer than 6%.
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers.
Which places near Ironwood share this climate record?
3 places have no NOAA station with 1991-2020 normals of their 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.
- Montreal, WI793 people · 5 mi SW
- Iron Belt, WI143 people · 10 mi SW
- Pence, WI139 people · 7 mi SW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Ironwood's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Ironwood. This page uses Ironwood #2; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Ironwood station USC00204104 | 2 mi W | 1,430 ft | 40.2°F | 4°F | 76°F | 37.4 | 186 | May 20 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Ironwood's climate
What is the coldest month in Ironwood?
January, with a normal high of 20°F and a normal low of 2°F. The warmest is July (77°F by day, 55°F at night).
Does it snow in Ironwood?
Yes. NOAA publishes no 1991-2020 snowfall normal for Ironwood's NOAA station; Ironwood's own co-op station Ironwood station records 186 inches of snow in a normal year.
What plant hardiness zone is Ironwood in?
The USDA's 2023 map puts Ironwood in zone 4b in ZIP code 54525, the nearest ZIP area.
How late can frost come in Ironwood?
In half of years the last 32°F night comes after May 19; in one year in ten it comes after June 3. Waiting until June 3 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Michigan climateThe statewide normals and every place in the state
- Hurley, WI2 miles from this station, 40.4°F a year
- Saxon, WI14 miles from this station, 41.3°F a year
- Mellen, WI25 miles from this station, 40.4°F a year
- Rest Lake, WI27 miles from this station, 39.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made