Duluth, Minnesota climate: Normal weather by month, frost dates and records
Duluth's normal year runs from 2°F January nights to 78°F July afternoons, with 31.2 inches of precipitation and 90 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 4.8°C, January lows of −16°C, July highs of 25°C, 792 mm of precipitation a year.
- NOAA stationDuluth International Airport
- Station IDUSW00014913
- Location46.84°N 92.21°W
- Elevation1,428 ft (435 m)
- From the center6 miles
- Population87,986
On October 23, the normal high in Duluth is 49°F and the normal low 33°F, and the chance of measurable rain or snow is 37%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Duluth.
- Jan 20° 2°
- Feb 25° 6°
- Mar 36° 18°
- Apr 49° 30°
- May 63° 41°
- Jun 72° 50°
- Jul 78° 56°
- Aug 76° 55°
- Sep 67° 47°
- Oct 53° 36°
- Nov 37° 23°
- Dec 25° 10°
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 Duluth each month?
July is the warmest month, with normal highs of 78°F; January the coldest, with normal lows of 2°F. The most precipitation falls in June (4.39 in), the least in January (0.95 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 20°F | 2°F | 11.2°F | 0.95 | 16.8 | 10 | <1 | 31 | 9 h |
| February | 25°F | 6°F | 15.4°F | 1.01 | 15.1 | 9 | <1 | 28 | 10 h 20 min |
| March | 36°F | 18°F | 27.0°F | 1.46 | 12.8 | 10 | <1 | 28 | 11 h 50 min |
| April | 49°F | 30°F | 39.5°F | 2.53 | 9.1 | 11 | <1 | 19 | 13 h 30 min |
| May | 63°F | 41°F | 52.0°F | 3.37 | 0.8 | 13 | <1 | 4 | 15 h |
| June | 72°F | 50°F | 61.2°F | 4.39 | 0.0 | 12 | <1 | <1 | 15 h 50 min |
| July | 78°F | 56°F | 67.0°F | 3.92 | 0.0 | 12 | 1 | <1 | 15 h 30 min |
| August | 76°F | 55°F | 65.5°F | 3.73 | 0.0 | 11 | 1 | <1 | 14 h 20 min |
| September | 67°F | 47°F | 57.2°F | 3.48 | 0.1 | 12 | <1 | 1 | 12 h 40 min |
| October | 53°F | 36°F | 44.1°F | 2.91 | 2.7 | 12 | <1 | 11 | 11 h |
| November | 37°F | 23°F | 29.8°F | 1.96 | 14.1 | 11 | <1 | 25 | 9 h 30 min |
| December | 25°F | 10°F | 17.1°F | 1.47 | 18.7 | 11 | <1 | 31 | 8 h 30 min |
| Year (annual) | 50°F | 31°F | 40.6°F | 31.18 | 90.2 | 133 | 2 | 177 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | −7°C | −16°C | −11.6°C | 24 mm | 43 cm |
| February | −4°C | −14°C | −9.2°C | 26 mm | 38 cm |
| March | 2°C | −8°C | −2.8°C | 37 mm | 33 cm |
| April | 10°C | −1°C | 4.2°C | 64 mm | 23 cm |
| May | 17°C | 5°C | 11.1°C | 86 mm | 2 cm |
| June | 22°C | 10°C | 16.2°C | 112 mm | 0 cm |
| July | 25°C | 13°C | 19.4°C | 100 mm | 0 cm |
| August | 24°C | 13°C | 18.6°C | 95 mm | 0 cm |
| September | 20°C | 8°C | 14.0°C | 88 mm | 0 cm |
| October | 12°C | 2°C | 6.7°C | 74 mm | 7 cm |
| November | 3°C | −5°C | −1.2°C | 50 mm | 36 cm |
| December | −4°C | −12°C | −8.3°C | 37 mm | 47 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014913; 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 Duluth?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, August 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 USW00014913.
When is the last frost in Duluth?
In Duluth, the last spring frost (32°F) comes after May 13 in half of years and after May 29 in one year in ten; the first autumn frost comes before October 1 in half of years and before September 18 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 131 year in 10 after May 29; 9 in 10 after April 29
- First autumn frost, half of years before
- October 11 year in 10 before September 18; 9 in 10 before October 16
NOAA puts the median frost-free season at 140 days, and the season without a hard freeze (28°F) at 165 days.
A hard freeze (28°F) comes after April 30 in half of springs and before October 13 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Duluth in zones 4b to 5a across its 9 ZIP code areas (4b in 55811, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Duluth's NOAA station is in zone 4b: the coldest night of a typical year reaches −24°F (30 complete years).
Frost dates for every NOAA station in Minnesota · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00014913; 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.
What hardiness zone is each Duluth ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Duluth's 9 ZIP code areas run from zone 4b to 5a: 8 in 4b and 1 in 5a. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Duluth?
In a normal year in Duluth, 2 days a year reach 90°F, 177 nights fall to 32°F or colder and 133 days bring measurable precipitation.
- Days at 90°F or more
- 2a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 177a normal year
- Days that stay below freezing
- 99high of 32°F or less
- Days with 0.01 inch of precipitation
- 133a normal year
- Days with 1 inch of snow or more
- 25a normal year
The highest temperature in Duluth's official record (kept by the National Weather Service since 1874) is 106°F, on July 13, 1936; the lowest is −41°F, on January 2, 1885.
The wettest calendar year on that record is 1879, with 45.38 in; the snowiest season is 2022–23, with 140.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00014913; records: ACIS (NOAA Regional Climate Centers), NWS threaded record DLHthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Duluth, and how clear are its skies?
The summer (June-August) dew point averages 55°F. The muggiest month is July, with an average dew point of 57°F; the driest air comes in January (6°F). April is the windiest month (10.9 mph on average), and July has the most clear or nearly clear hours (58%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 6°F | 74% | 62% | 10.1 mph | 46% | 40% |
| February | 11°F | 70% | 58% | 10.3 mph | 49% | 38% |
| March | 22°F | 65% | 52% | 10.7 mph | 47% | 35% |
| April | 30°F | 57% | 43% | 10.9 mph | 52% | 28% |
| May | 44°F | 64% | 50% | 9.4 mph | 49% | 25% |
| June | 55°F | 70% | 56% | 9.2 mph | 51% | 23% |
| July | 57°F | 72% | 54% | 8.1 mph | 58% | 15% |
| August | 54°F | 75% | 57% | 9.0 mph | 58% | 20% |
| September | 41°F | 72% | 56% | 10.0 mph | 52% | 30% |
| October | 29°F | 72% | 59% | 10.5 mph | 40% | 44% |
| November | 16°F | 78% | 69% | 10.5 mph | 38% | 47% |
| December | 7°F | 77% | 68% | 10.6 mph | 44% | 44% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014913. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Duluth?
Over a year 72% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Duluth, 3.7 kWh per square metre a day. July is the sunniest month (79%) and December the cloudiest (60%). Among the 459 U.S. places of 50,000 or more, that ranks tied 385th (with 30 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 70% | 1.6 |
| February | 76% | 2.7 |
| March | 73% | 3.8 |
| April | 69% | 4.7 |
| May | 68% | 5.4 |
| June | 72% | 5.9 |
| July | 79% | 6.2 |
| August | 77% | 5.2 |
| September | 72% | 3.8 |
| October | 65% | 2.4 |
| November | 63% | 1.5 |
| December | 60% | 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 Duluth need?
A normal year in Duluth brings 9,115 heating degree days, 70% more than the median U.S. place (5,373), and 255 cooling degree days, 72% 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 1,789 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,669 | 0 |
| February | 1,389 | 0 |
| March | 1,178 | 0 |
| April | 764 | 0 |
| May | 410 | 7 |
| June | 152 | 36 |
| July | 50 | 110 |
| August | 64 | 80 |
| September | 254 | 21 |
| October | 647 | 1 |
| November | 1,056 | 0 |
| December | 1,483 | 0 |
| Year (annual) | 9,115 | 255 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014913. 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 Duluth been warmer than normal lately?
2025 averaged 40.5°F, 0.1°F below the 1991-2020 normal of 40.6°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 43.1°F | +2.5°F | 25.71 | 60.1 |
| 2022 | 38.7°F | −1.9°F | 34.06 | 124.9 |
| 2023 | 42.5°F | +1.9°F | 32.99 | 85.0 |
| 2024 | 44.6°F | +4.0°F | 28.00 | 44.6 |
| 2025 | 40.5°F | −0.1°F | 20.35 | 68.3 |
Over 76 complete years from 1948 to 2025, the station's annual mean temperature rose at a fitted 4.6°F per century (+0.26°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00014913; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Duluth's climate compare?
Duluth is warmer than 37 of the other 128 places with their own NOAA record in Minnesota, and wetter than 74. Across the 7,247 U.S. stations with normals, its annual mean of 40.6°F is warmer than 7%.
In the Köppen classification computed from these normals, Duluth 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 Duluth share this climate record?
Superior 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.
- Superior, WI668 people · 14 mi S
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 Duluth's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Duluth. This page uses Duluth International Airport; the other differs by site and elevation:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Duluth Harbor Station USC00212246 | 2 mi E | 610 ft | 40.8°F | 4°F | 75°F | – | – | May 14 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Duluth's climate
What is the coldest month in Duluth?
January, with a normal high of 20°F and a normal low of 2°F. The warmest is July (78°F by day, 56°F at night).
Does it snow in Duluth?
Yes: 90 inches in a normal year, falling on 62 days with 0.1 inch or more, the most in December (18.7 inches).
What is the rainiest month in Duluth?
June, with 4.39 in of precipitation in a normal year; the driest is January with 0.95 in.
What plant hardiness zone is Duluth in?
The USDA's 2023 map puts Duluth in zones 4b to 5a across its 9 ZIP code areas (4b in 55811, the largest). By the same method at Duluth's NOAA station, the coldest night of a typical year reaches −24°F (30 years, 1991-2020): zone 4b.
How late can frost come in Duluth?
In half of years the last 32°F night comes after May 13; in one year in ten it comes after May 29. Waiting until May 29 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Duluth in OctoberThis month day by day, its records and recent years
- Minnesota climateThe statewide normals and every place in the state
- Hermantown, MN0 miles from this station, 39.7°F a year
- Superior, WI10 miles from this station, 41.4°F a year
- Island Lake (4 mi E), MN14 miles from this station, 38.9°F a year
- Cloquet, MN17 miles from this station, 39.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made