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Heather’s Weather Whys: How fall can bring cool nights in a hot pattern

Summer heat waves can be brutal, both day and night. But the story is a little different for hot weather in September.
Credit: WGRZ

BUFFALO, N.Y. — Summer 2020 brought the heat, both day and night.

We can still get plenty of warm days in the fall, even as the days get shorter but it’s actually the longer nights that can make a late-season run at 90 degrees feel tolerable.

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The length of darkness in a given day is part of the reason. During the height of summer, we experience a much longer amount of daylight than we do in September and October.

So this time of year, nights are anywhere from two to three hours longer, depending on how late into the seasons you compare. Longer nights mean longer periods for cooling and cooler temperatures as a result.

RELATED: Heather’s Weather Whys: the summer solstice

Another big reason nights in an autumn heatwave can cool down is humidity. Or really, a lack of humidity during the fall. Less moisture gets pulled this far north this time of year, so the air has less water vapor in it.

Water vapor particles can hang onto energy from the sun longer than air molecules, so if there’s more moisture, there’s more water vapor and there’s more ability for Earth’s lower atmosphere to stay warmer at night.

Scientifically put, humid air has a higher heat capacity than dry air.

Like it or not, the longer nights and decreased sun angle will eventually win out, and we’ll say goodbye to the heat we’ve held onto for the entire summer. So enjoy the warmth while it’s here!

New episodes of Heather’s Weather Whys are posted to the WGRZ YouTube channel every Wednesday evening. You can also watch on Thursdays at 5:30 p.m. on Channel 2 News.

If you have a weather question for Heather to answer, send it to her at heather.waldman@wgrz.com or connect with her on Facebook or Twitter.

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