With Autumn Comes Fog Season for Northern States

By By Gina Cherundolo, AccuWeather.com Staff Writer
October 11, 2011, 3:58:38 AM EDT

As autumn kicks off, fall foliage and cooler temperatures won't be the only changes you'll notice outside. Fog season is now well under way over the northern states.

Other regions of the U.S. have similar fog seasons, but these take place at different times of the year. The Gulf Coast, for example, has a fog season in the middle of winter, when storms passing to the north draw out moisture from the Gulf.

"Dense fog can occur any time of the year, given the right atmospheric conditions," said AccuWeather.com Expert Senior Meteorologist Alex Sosnowski.

Fog season for the northern regions falls typically between late August and the end of October. According Sosnowski, this time of year has perfect conditions for radiation fog.


Fog forms when the difference between the air temperature and the dew point, the temperature at which dew forms, is generally less than four degrees Fahrenheit.

As the nights become longer, the air temperature is more likely to dip close to the dew point.

These longer nights, combined with light winds and lingering humidity in the air from bodies of water and moisture in the soil, produce foggy conditions in the autumn season.

Since the lowest temperature of the day occurs right around sunrise, this leads to the fog being most common in the morning hours.

This can make travel dangerous, both on the ground and in the air. According to a study by NOAA, about 700 fog-related highway fatalities occur in the United States each year.

As the autumn season progresses, the humidity in the air decreases and winds become stronger, making fog far less common.

In the words of AccuWeather.com's Elliot Abrams, "Once the fog is gone, it won't be 'mist.'"

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