Discover The 15 Coldest States In September

Written by Shreya Agrawal
Updated: September 12, 2023
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September is typically associated with the transition from summer to autumn. However, across the country, it offers a fascinating spectrum of temperatures. While some regions still have the warmth of late summer, others experience a noticeable chill in the air as they prepare for the impending fall season. Here, we explore the top 15 coldest states in September, which are ranked by the lowest temperatures they commonly encounter during September.

New Hampshire’s September temperatures have average highs around 60°F and nighttime lows in the upper 30°F.

1. Alaska

Top view of Juneau - Alaska - USA

A scenic view of Gastineau Channel, Douglas Island, and Downtown Juneau from the top of Mt. Juneau in Alaska during Summer.

©ad_foto/ via Getty Images

It should come as no surprise that Alaska tops our list as the coldest state in September. With its vast expanse and northerly location, Alaska experiences frigid temperatures, especially in its northern and interior regions. In some areas, temperatures can drop below freezing, with Barrow and Fairbanks frequently recording temperatures between 20-30°F during September nights.

Average Temperature

September temperatures in Alaska vary significantly based on the region. In the southern coastal areas like Anchorage, the average highs range from 50°F to 60°F, while the northern cities such as Barrow and Fairbanks experience average highs in the 30-50°F. Nighttime lows can drop well below freezing.

Coldest Temperature on Record

The coldest temperature ever recorded in Alaska occurred on January 23, 1971, in Prospect Creek Camp, where the mercury plummeted to a chilling -80°F.

Population

Alaska, despite its vast size, is sparsely populated. In 2021, it had a population of approximately 731,000 people. Consequently, its population density is one of the lowest in the United States.

Wildlife

Alaska is also renowned for its diverse wildlife. The state is home to iconic species like grizzly bears, moose, bald eagles, and wolves. The cold temperatures in September, therefore, mark the beginning of the salmon spawning season, drawing brown bears to the rivers to feast on this essential food source.

2. Montana

The Gallatin River as it runs through the western most part of Yellowstone National Park along Highway 191 in Montana, United States of America

The Gallatin River as it runs through the westernmost part of Yellowstone National Park along Highway 191 in Montana.

©Harry Beugelink/Shutterstock.com

Montana is known for its rugged landscapes and dramatic weather changes. It is also the second coldest state in September. As fall approaches, temperatures plummet, especially in the mountainous regions. Places like Butte and Helena can experience overnight lows in the low 30s°F, reminding residents that winter is just around the corner.

Average Temperature

In September, Montana experiences a significant temperature drop from the summer. Average highs range from 60-70°F in the west, including Missoula, to 50-60˚F in places like Butte and Helena. Nighttime lows often dip into the 30s and 40s in degrees Fahrenheit.

Coldest Temperature on Record

Montana’s lowest recorded temperature occurred on January 20, 1954, in Rogers Pass, a frigid -70°F.

Population

Montana had a population of approximately 1.08 million people in 2021. Despite its large land area, it is one of the least densely populated states in the U.S.

Wildlife

Montana’s diverse ecosystems support a range of wildlife. In September, visitors might spot elk and deer preparing for the mating season, while bighorn sheep roam the mountains. Birdwatchers can also enjoy sightings of bald eagles, golden eagles, and various migratory species passing through.

3. Wyoming

The Snowy Range of southwestern Wyoming in early winter. Medicine Bow-Routt National Park. Snowy Range in Wyoming's Medicine Bow Wilderness. Boulders, trees, snow and sheer rock faces.

The Snowy Range of Medicine Bow-Routt National Park in southwestern Wyoming in early winter. It is surrounded by boulders, trees, snow, and sheer rock faces.

©Rexjaymes/Shutterstock.com

Wyoming, another state with significant elevation variations, ranks third on our list. Places like Casper and Cheyenne often see September lows in the low 30-40°F. The higher-altitude areas, like Yellowstone National Park, can even witness sub-freezing temperatures.

Average Temperature

September in Wyoming brings cooler temperatures, with average highs ranging from the 60s˚F in cities like Casper and Cheyenne to the 50s˚F in Yellowstone National Park. Nighttime lows often drop into the 30s and 40s in degrees Fahrenheit.

Coldest Temperature on Record

The state’s record low occurred on February 9, 1933, in Moran, dropping to -66°F.

Population

Wyoming had a population of approximately 580,000 people in 2021. It’s the least populous state in the country, known for its wide-open spaces.

Wildlife

Wyoming is famous for its national parks, including Yellowstone and Grand Teton, teeming with wildlife. September is therefore an excellent time to witness the elk rut in Yellowstone, with bugling elk echoing through the valleys. Visitors might also encounter bison, grizzly bears, and pronghorn in their natural habitats.

4. Idaho

The Portneuf River, popular for floating and swimming, is a tributary of the Snake River in Southwestern Idaho that winds for 124 miles.

©Decumanus / CC BY-SA 3.0 – License

Idaho, with its diverse geography ranging from fertile valleys to lofty peaks, comes in fourth place. In cities like Boise and Coeur d’Alene, September nights can be quite chilly, with temperatures hovering around the mid-30s in degrees Fahrenheit. The higher elevations in the state, including Sun Valley, can experience even colder conditions.

Average Temperature

In September, Idaho experiences a cooling trend, with average highs ranging from the 60s˚F in cities like Boise to the 50s˚F in higher-elevation areas like Sun Valley. Nighttime lows can also dip into the 30s and 40s in degrees Fahrenheit.

Coldest Temperature on Record

The coldest temperature recorded in Idaho was -60°F in Island Park Dam on January 18, 1943.

Population

As of 2021, Idaho had a population of around 1.8 million people, making it one of the fastest-growing states in the U.S.

Wildlife

Idaho has diverse wildlife, including populations of elk, mule deer, and white-tailed deer. In September, the state’s forests and mountains come alive with the vibrant colors of fall, thus providing a stunning backdrop for observing these animals in their natural habitats.

5. Vermont

Lake Champlain and the Blue Mountains of Vermont

Lake Champlain and the Blue Mountains of Vermont.

©Guy Banville/ via Getty Images

Located in the northeastern part of the United States, Vermont is the fifth one on the list. As the Green Mountain State transitions into fall, places like Burlington and Montpelier can experience September lows in the upper 30s°F. The onset of foliage season adds to the charm of this chilly month.

Average Temperature

September in Vermont has average highs in the 60s°F and nighttime lows in the upper 30s°F. Cities like Burlington and Montpelier experience these cooler temperatures, which are perfect for enjoying the changing foliage.

Coldest Temperature on Record

Vermont’s record low was -50°F in Bloomfield on December 30, 1933.

Population

Vermont’s population was approximately 623,000 people as of 2021. It is one of the smallest and least populous states in the U.S.

Wildlife

Vermont’s woodlands and wetlands provide habitat for various wildlife species, including white-tailed deer, black bears, and moose. September marks the beginning of the deer rut, making it an excellent time for wildlife enthusiasts to observe these majestic creatures.

6. New Hampshire

New Forest wild pony at Sunrise, Godshill, Hampshire

A wild pony at Sunrise, Godshill, Hampshire

©Claire Sheppard/iStock via Getty Images

New Hampshire, nestled in the heart of New England, follows closely behind Vermont in terms of September chill. Cities like Concord and Manchester can witness overnight lows in the upper 30s°F.

Average Temperature

New Hampshire’s September temperatures have average highs around 60°F and nighttime lows in the upper 30°F. Cities like Concord and Manchester embrace autumn, visible in the leaves changing colors.

Coldest Temperature on Record

The state’s record low was -47°F in Berlin on January 22, 1885.

Population

New Hampshire had a population of approximately 1.37 million people in 2021, making it one of the smaller states in terms of population.

Wildlife

New Hampshire also offers opportunities for wildlife enthusiasts to spot black bears, bobcats, and wild turkeys. September’s cooler temperatures also mark the start of bird migration. During this time, waterfowl like ducks and geese make their way through the state.

7. Maine

Shops lining Old Orchard Beach pier in Maine

Old Orchard Beach in Maine has been a popular family destination for over 100 years.

©Paul VanDerWerf / CC BY 2.0 – License

Maine ranks seventh on our list. In cities like Portland and Bangor, September temperatures often dip into the upper 30s°F. The state’s northern reaches, including Presque Isle, can experience even colder nights.

Average Temperature

In September, Maine experiences average highs in the 60s°F and nighttime lows in the upper 30s°F. Cities like Portland and Bangor also embrace the changing seasons as fall settles in.

Coldest Temperature on Record

Maine’s record low was -50°F in Clayton Lake on January 16, 2009.

Population

In 2021, Maine had a population of approximately 1.34 million people. Its vast forests and picturesque coastline attract residents and tourists, but it still remains small and sparsely populated.

Wildlife

Maine’s wilderness areas are also home to an array of wildlife, including moose, white-tailed deer, and bald eagles. September marks the onset of the moose rut. Thus, it provides wildlife enthusiasts a chance to witness these massive mammals in their natural behavior.

8. South Dakota

Wind Cave National Monument, South Dakota

©Murray Foubister / CC BY-SA 2.0 – License

South Dakota is located in the northern Plains and secures the eighth spot on our list. In places like Rapid City and Pierre, September lows frequently fall into the low 40s°F. As summer fades away, residents prepare for the cooler months ahead.

Average Temperature

South Dakota sees a transition to cooler weather in September with average highs in the 60s°F and nighttime lows in the low 40s °F. Cities like Rapid City and Pierre prepare for the arrival of autumn by shedding leaves off of trees.

Coldest Temperature on Record

The state’s record low was -58°F in McIntosh on February 17, 1936.

Population

South Dakota had a population of around 900,000 people in 2021. Its vast landscapes and historic sites draw visitors year-round, yet it has a small population.

Wildlife

South Dakota is also famous for its Badlands and the wildlife that calls it home, including bison, pronghorn, and coyotes. September is therefore an excellent time for birdwatchers. During this time, numerous species of waterfowl and raptors pass through the state during their fall migration.

9. North Dakota

The banks of the Red River in Grand Forks, North Dakota.

©Tony Webster / CC BY-SA 2.0 – License

North Dakota, its neighbor to the north, also experiences a considerable chill in September, making it our ninth coldest state. Cities like Bismarck and Fargo often see nighttime temperatures in the low 40s °F.

Average Temperature

North Dakota experiences cooler September temperatures with average highs in the 60s°F and nighttime lows in the low 40s°F.

Coldest Temperature on Record

North Dakota’s record low was -60°F in Parshall on February 15, 1936.

Population

North Dakota had a population of approximately 770,000 people in 2021. Its vast prairies and agricultural landscapes define the state and also ensure a small population.

Wildlife

North Dakota’s grasslands also provide critical habitat for a variety of wildlife, including pronghorn, mule deer, and pheasants. In September, waterfowl hunters also flock to the state to pursue ducks and geese during their fall migration.

10. Minnesota

View of the upper falls of Minneopa Falls waterfall at Minneopa State Park in Mankato Minnesota

View of the upper falls of Minneopa Falls waterfall at Minneopa State Park in Mankato, Minnesota.

©melissamn/Shutterstock.com

Minnesota, with its multitude of lakes and forests, ranks tenth on our list. As September arrives, cities like Minneapolis and Duluth can experience overnight lows in the low 40s °F. The changing leaves reflect the onset of fall in this northern state.

Average Temperature

September in Minnesota means average highs in the 60s °F in cities like Minneapolis and Duluth. Nighttime lows can often drop into the low 40s˚F.

Coldest Temperature on Record

The state’s record low was -60°F in Tower on February 2, 1996.

Population

In 2021, Minnesota had a population of approximately 5.7 million people. Its numerous lakes and outdoor recreational opportunities also attract residents and tourists. This means that despite its cold weather, the state still appeals to a lot of people.

Wildlife

Minnesota’s forests, lakes, and wetlands are also home to a wide range of wildlife, including white-tailed deer, black bears, and loons. September is therefore a prime time for birdwatching. This is because migratory birds such as warblers and sandhill cranes pass through the state.

11. Colorado

Colorful Trees along the Animas River in Colorado

Colorful trees line the banks of the Animas River in Colorado.

©Kent Raney/ via Getty Images

Colorado, known for its stunning Rocky Mountains, comes in eleventh place. While the state’s lower elevations in cities like Denver may not experience extreme cold in September, areas like Aspen and Vail can see temperatures dip into the low 40s°F. Therefore, this assists with the winter sports season in the few months ahead.

Average Temperature

Colorado’s September weather varies by elevation. In cities like Denver, average highs are in the 70s°F, while in high-altitude areas like Aspen and Vail, highs may only reach the 60s°F. Nighttime lows can also drop into the 30s°F.

Coldest Temperature on Record

The state’s record low was -61°F in Maybell on February 1, 1985.

Population

Colorado had a population of approximately 5.8 million people in 2021. Its diverse landscapes, including the Rocky Mountains, also draw residents and outdoor enthusiasts. This is what contributes to the relatively large population of the state.

Wildlife

Colorado’s mountains are also inhabited by iconic species like elk, mule deer, and bighorn sheep. September is therefore a popular time for elk mating rituals, with the bugling calls of bull elk echoing through the high country.

12. Wisconsin

Cana Island Lighthouse

The Cana Island Lighthouse is located in Baileys Harbor, Wisconsin on Lake Michigan.

©John Touscany/iStock via Getty Images

Wisconsin is a state known for its cheese as well as its picturesque landscapes. Therefore, it secures the twelfth position on our list of the coldest states in September. Cities like Milwaukee and Madison often experience September lows in the low 40s°F, as they set the stage for autumn’s arrival.

Average Temperature

September in Wisconsin sees average highs in the 60s°F and nighttime lows in the low 40s°F in cities like Milwaukee and Madison. Fall colors start to appear, setting a picturesque scene in the state.

Coldest Temperature on Record

The state’s record low was -55°F in Couderay on February 2, 1996.

Population

Wisconsin had a population of approximately 5.8 million people in 2021. The state is known for its dairy production and outdoor recreational opportunities and therefore, has a high population.

Wildlife

Wisconsin’s forests and lakes also provide habitat for white-tailed deer, black bears, and a variety of bird species. September is, therefore, an excellent time for birdwatching, as migratory birds pass through on their way south for the winter.

13. Oregon

East Lake, Oregon at sunset with mountains in the background

East Lake, Oregon at sunset with mountains in the background.

©Jared Abell/Shutterstock.com

Oregon, with its diverse geography spanning from the Pacific coastline to the Cascade Mountains, ranks thirteenth in the list of the coldest states in September. In cities like Portland and Eugene, September nights can be chilly, with temperatures hovering around the mid-40s°F. The state’s higher elevations, including Mount Hood, can experience even colder conditions.

Average Temperature

In September, Oregon’s coastal areas like Portland experience average highs in the 60s°F, while cities like Eugene have highs in the 70s°F. Nighttime lows often drop into the 40s°F.

Coldest Temperature on Record

The state’s record low was -54°F in Seneca on February 10, 1933.

Population

In 2021, Oregon had a population of approximately 4.2 million people. The state’s natural beauty, including Crater Lake and Mount Hood, attracts residents and visitors. However, the state’s residents, while numerous, are still very protective of their natural lands.

Wildlife

Oregon’s diverse ecosystems are also home to a variety of wildlife, including black-tailed deer, cougars, and bald eagles. September is therefore a great time for birdwatchers like in other states, as migratory birds stop over in Oregon’s wetlands and forests.

14. Michigan

Tahquamenon Falls

A panoramic view of the very picturesque Tahquamenon Falls and Tahquamenon River during Autumn, Upper Peninsula, Michigan, USA

©DougLemke/iStock via Getty Images

Michigan is surrounded by the moderating power of the Great Lakes. Yet, it is our fourteenth coldest state in September. Cities like Detroit and Lansing typically experience nighttime temperatures in the mid-40s°F. As the summer tourism season winds down, locals and visitors alike embrace the cooler weather.

Average Temperature

September in Michigan brings cooler temperatures with average highs in the 60s°F in cities like Detroit and Lansing. Nighttime lows can drop into the low 40s°F.

Coldest Temperature on Record

The state’s record low was -51°F in Vanderbilt on February 9, 1934.

Population

In 2021, Michigan had a population of about 10 million people. The state is known for its Great Lakes, forests, and automotive industry, and these also contribute to its huge population for its small size.

Wildlife

Michigan’s forests and lakes also support a variety of wildlife, including white-tailed deer, black bears, and loons.

15. Washington

Renton Park Lake Shoreline 3, Lake Washington, Washington State

A view of the shoreline at Gene Coulon Park in Renton, Washington.

©gmc3101/iStock via Getty Images

Last one on our list of the top 15 coldest states in the country is Washington, the Evergreen State, which often experiences cool September nights. In cities like Seattle and Olympia, temperatures can drop into the mid-40s°F, signaling the start of the rainy season in the Pacific Northwest.

Average Temperature

September in Washington means average highs in the 60s°F in cities like Seattle and Olympia. Nighttime lows can drop into the mid-40s°F. This is also when the rainy season begins.

Coldest Temperature on Record

The state’s record low was -48°F in Winthrop on December 30, 1968.

Population

In 2021, Washington had a population of approximately 7.8 million people. The state’s diverse landscapes, including the Olympic Peninsula and Cascade Range, attract residents and tourists. This also contributes to the state’s huge population.

Wildlife

Washington’s ecosystems are home to species like Roosevelt elk, black bears, and bald eagles. September marks the start of salmon spawning, drawing in predators like orcas and bald eagles to feed on them.

Summary Table of the Top 15 Coldest States in September

RankStateAverage Temperature in September (°F)Coldest Temperature on Record (°F)Wildlife Overview
1Alaska43.6-80Diverse wildlife, including bears, moose, and bald eagles.
2Montana57.1-70Home to bison, elk, and mountain goats, with Yellowstone National Park.
3Wyoming57.7-63Offers habitat for bison, pronghorn, and grizzly bears.
4Idaho61.2-60Features diverse ecosystems, including forests and high mountain ranges.
5Vermont61.3-50Abundant wildlife, including white-tailed deer, moose, and black bears.
6New Hampshire63.3-50Home to white-tailed deer, foxes, and various bird species.
7Maine61.2-48Features extensive forests and is known for its lobster industry.
8South Dakota63.5-58Bison herds roam the prairies, and the Black Hills offer diverse wildlife.
9North Dakota62.7-60Prairies and badlands support bison, pronghorn, and coyotes.
10Minnesota63.9-60Home to moose, wolves, and loons, with numerous lakes and forests.
11Colorado66.5-61Diverse ecosystems with elk, mule deer, and mountain lions.
12Wisconsin63.1-55Abundant wildlife, including white-tailed deer and black bears.
13Oregon64.3-54Diverse ecosystems with black-tailed deer, cougars, and bald eagles.
14Michigan62.2-51Known for the Great Lakes and wildlife like black bears and loons.
15Washington65.1-48Diverse landscapes host Roosevelt elk, black bears, and bald eagles.
Summary Table of the 15 Coldest States In September

The photo featured at the top of this post is © CherylRamalho/Shutterstock.com


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About the Author

Shreya is a climate scientist. She also studies paleontology and evolutionary biology. She enjoys reading all kinds of literature and listening to rock music in her free time.

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