More daylight is lost in September than in any other month of the year, according to AccuWeather

Daylight will soon start disappearing remarkably fast.

With the winding down of summer comes that familiar shortening of daylight hours until we reach the autumn equinox, one of two points in our annual calendar when days and nights will be roughly equal lengths. Days have been getting subtly shorter since the summer solstice June 20, but that loss of daylight will become much more noticeable in September.

Americans in many parts of the country can expect more daylight to disappear in September than any other month of the year, according to AccuWeather meteorologists. In the northernmost areas of the United States, daylight hours will shorten by about 100 minutes over the month. The loss of daylight in Alaska will be most dramatic at 193 minutes.

Here's what to know:

Why do we lose daylight in the fall?

The reason we see variations in daylight throughout the year has to do with the tilt of the Earth's axis and whether it is toward or away from the sun. There are two times during the Earth's rotation of the sun over the course of a year that the axis of the Earth is tilted neither toward or away from the sun; we call them equinoxes.

The fall equinox happens in September, and this year it falls on Sept. 22 at 2:19 p.m. ET, scientists say. When it happens, if you happen to be along the Earth's equator, you would be able to see the sun directly overhead at noon.

On the equinox, the "'nearly' equal hours of day and night is due to refraction of sunlight or a bending of the light's rays that causes the sun to appear above the horizon when the actual position of the sun is below the horizon," according to the National Weather Service.

Earth orbits the sun at an angle, so in the northern hemisphere, where the United States is, Earth is tilted toward the sun during summer and away during winter, while the southern hemisphere is experiencing the opposite. After the spring equinox in March, we experience lengthening days because the Earth's axis is gradually tilting our hemisphere more toward the sun until it reaches maximum tilt, which we call summer solstice.

Then our hours of daylight shorten until we reach the fall equinox and the days and nights are roughly equal lengths. This shortening continues until winter solstice in December, when we'll experience the shortest day and longest night.

How will the days change in September?

Daylight will be shorter by the end of September by an hour or more for many parts of the United States. Even in southern locations, more than 40 minutes is expected to be shaved off daytime, according to AccuWeather. Here's how much daylight will be lost in some U.S. cities:

  • Miami: 43 minutes
  • Austin: 52 minutes
  • San Diego: 58 minutes
  • Raleigh, North Carolina: 64 minutes
  • New York: 77 minutes
  • Portland, Oregon: 91 minutes
  • International Falls, Minnesota: 102 minutes

The loss of daylight will usher in cooler weather, even dropping temperatures to below historical averages for large parts of the nation, AccuWeather senior meteorologist Isaac Longley told USA TODAY in an email.

"With such a large loss in daylight, fall-like weather can arrive quickly in September. This year will be no exception, with cool air spilling southward out of Canada and into the central and eastern U.S. through the first week or so," Longley said. A return to summerlike weather is still possible across the northern tier of the country later in September, he added.

Forecasters with the National Weather Service said Labor Day weekend will see fall-like temperatures in regions that include the Great Lakes, Northeast, Mid-Atlantic and Ohio Valley, with afternoon highs in the 60s and 70s.

This article originally appeared on USA TODAY: Daylight is about to rapidly disappear. Why September robs us of so much sun.

Reporting by Jeanine Santucci, USA TODAY / USA TODAY

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