Signs Of Fall That Can Appear In August

Linda Lam
Published: August 9, 2017

By August, some begin to look forward to cooler temperatures and the other changes that fall brings.

In some areas of the U.S., you can even see signs that fall is, in fact, right around the corner.

(MORE: Fall 2017 Temperature Outlook)

Frost and Freeze In August?

The peak of summer heat begins to wane as August progresses and by the end of the month temperatures noticeably begin to cool in some areas.

Average low temperatures for the month are in the 40s and 50s from the Pacific Northwest into the intermountain West, as well as into the Upper Midwest and northern New England. But depending on the weather pattern, temperatures can dip below average at times.

(MORE: Average Temperatures)

In fact, there are many areas of the northern U.S. that has experienced temperatures of 32 degrees or lower in August.

Not surprisingly, many of these locations are in the higher elevations. This includes Missoula, Montana, which has recorded temperatures at or below 32 degrees in August nine times in seven years. Great Falls, Montana, has seen freezing temperatures in August only four times, all in 1992.

Farther south, Boise, Idaho, has only seen the 32-degree mark once in August, back in 1892. Casper, Wyoming, also has recorded  only one freezing temperature in August, 29 degrees on Aug.t, 23, 2015. However, in some areas frost and freezes are much more common including in Evanston, Wyoming, which has seen the mercury plunge to 23 degrees in August.

Although freezing conditions are not common in the northern Plains and Upper Midwest in August, they have been recorded. International Falls, Minnesota has reached freezing 12 times in 11 years. Duluth, Minnesota, has reached this mark only once, in 1986.

The lowest August temperature on record in Bismarck, Fargo ,and Grand Forks, North Dakota, is 32 degrees and has been reached only once or twice for each city.

(MORE: When Your First Freeze Typically Arrives)

Farther east, Sault Ste. Marie, Michigan has seen temperatures drop below the freezing mark twice, most recently on Aug. 29, 1982, when it dipped to 29 degrees. That is also the coldest temperature recorded in August in Concord, New Hampshire, which has seen temperatures plummet to 32 degrees or colder three times.

These early frost and freeze dates are not normal occurrences as most of these areas wait until at least mid-September for the first freeze on average. However, if an unusually strong upper-level trough, or southward dip in the jet stream, for August moves southward into the U.S. then colder-than-average temperatures can result in a very early frost or freeze.

It is also important to note that areas outside of cities tend to experience colder temperatures as the daytime warmth tends to be lost quicker in more rural areas, due to the urban heat island effect. 

Leaves Begin To Change Color

One of the biggest signs of fall that many look forward to is the leaves changing color.

In most years the peak of fall foliage does not begin until late September, but depending on weather conditions and location some leaves can begin to turn colors as early as late August.

One exception is Alaska, where leaves change in August. Otherwise, for most of the contiguous U.S. foliage changes in August are not normally expected.

Leaves begin to change color in response to the cooler temperatures and longer nights. However, weather conditions, such as drought, can lead to leaves changing color and falling early.

A prolonged period of unusually cold temperatures in mid-to-late August can result in some leaves changing color early.

(MORE: When Does Your City See Peak Fall Color)

In general, some of the higher elevations of the Rockies and northern New England begin to show early signs of brightly colored leaves by the end of August, but you will need to wait until September for peak foliage in these areas.

Snow In The Mountains

Snow becomes a fairly typical occurrence in late August in the highest peaks of the Rockies, especially the Canadian Rockies.

Early August snow is a little more unusual, but snow was spotted on top of Pikes Peak and Mount Massive in the Colorado Rockies late Sunday into Monday this week. Pikes Peak is at an elevation of 14,115 feet making it the highest summit in the southern Rockies.

This snow was the result of a persistent and unusually strong upper-level trough that has brought colder-than-average temperatures to portions of the central and eastern U.S. to start August.

Snow has also fallen not just in the highest elevations in August. Great Falls, Montana, saw its earliest snow on Aug. 22, 1992, the same year its only below-freezing temperatures were recorded in August. 

(MORE: When the First Snow of the Season Typically Falls)

In the East, Mount Washington has recorded snow in August, with an average of 0.1 inches falling during the month. The most snow measured in August here was 2.5 inches in 1965.

Elsewhere, portions of Alaska, of course, measure snow in August. Utqiaġvik, formerly known as Barrow, typically sees its first measurable snow, at least 0.1 inches, on Aug. 23, based on the latest 30-year average from 1981-2010. Fairbanks experiences its first measurable snow in late September, but has recorded snow as early as Aug. 25, in 1995.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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