What is 'June gloom' and how does it affect Southern California?

The phenomenon known as "June gloom" plays a major role in altering the climate of coastal regions of Southern California when compared to areas just a few dozen miles farther inland.

June gloom refers to a band of low clouds and fog, known as the marine layer, that develops on an almost daily occurrence within a few miles of the southern California coastline during the overnight and morning hours.

"June gloom is so named as June can be one of the months that tends to have more persistent marine clouds than any other month," AccuWeather Western U.S. Weather Expert Ken Clark said.

"This phenomenon can really occur any month, especially from May through September, but it's the persistence that is why we talk about this during the month of June," he added.

June Gloom Static

The marine layer is created by rising air over the hot, desert regions of the Southwest. This rising air creates a vacuum. Cool, moist air is then drawn in from the Pacific Ocean along the coastline of California by a subtle breeze.

This cool, moist ocean flow leads to the formation of low clouds once the sun goes down and temperatures begin to fall. When the temperature dips to a certain point but the amount of moisture in the air holds steady, the humidity rises and clouds begin to form.

Once humidity reaches its maximum level, these clouds can thicken and lower, and fog can also form.

It is when the temperature difference between the ground and areas higher up in the atmosphere is greatest that the marine layer takes the longest to burn off.

"During the late morning and afternoon on most days, sunshine above the clouds helps to drag drier air higher into the atmosphere down to the surface, thus scouring out the clouds," AccuWeather Senior Meteorologist Alex Sosnowski said.

Once this process reverses after sundown, the marine layer tends to return and thicken, Sosnowski said.

"The marine layer can lead to huge differences in temperature between the coast to areas farther inland due to the delayed clearing at the coast, and it's not uncommon to have it cloudy and in the 60s at the beaches while it's in the 80s or even 90s only 10-20 miles inland," according to Clark.

See more summer weather so far this season: 

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Summer weather across the US in 2018
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Summer weather across the US in 2018
WELLFLEET, MA - JUNE 21: Mark Wilke and his wife Sharon enjoy the first day of summer at White Crest Beach in Wellfleet, MA on June 21, 2018. (Photo by Craig F. Walker/The Boston Globe via Getty Images)
ARLINGTON, VA - JUNE 20: A pedestrian passes near the Netherlands Carillon as the Washington Monument and United States Capitol are seen at sunrise on Wednesday June 20, 2018 in Arlington, VA. The summer solstice is Thursday. (Photo by Matt McClain/The Washington Post via Getty Images)
Pedestrians watch sailboats and windsurfers on the Charles River on the summer solstice in Boston, Massachusetts, U.S., June 21, 2018. REUTERS/Brian Snyder
A women keeps in the shade of her umbrella as she tries to beat the heat at Cardiff State beach in Encinitas, California, U.S. July 6, 2018. REUTERS/Mike Blake
A man cools off in fountain on the Rose Kennedy Greenway during a summer heat wave in Boston, Massachusetts, U.S., July 2, 2018. REUTERS/Brian Snyder
OLD ORCHARD BEACH, ME - JULY 4: Ryan Parsons, left, of Unity watches as his daughter, Lily, 10, rides the waves on her inflatable whale at Old Orchard Beach on a hot, beautiful Fourth of July. The Parson family was spending the day at the beach keeping cool and watching the fireworks. (Staff photo by Jill Brady/Portland Press Herald via Getty Images)
NEW JERSEY, USA - JUNE 30: People enjoy Manhattan skyline at the Hamilton Park during the hot weather in New Jersey, United States on June 30, 2018. (Photo by Atilgan Ozdil/Anadolu Agency/Getty Images)
NEW YORK, July 2, 2018 -- People cool themselves at a fountain at Washington Square Park in New York City, the United States, on July 2, 2018. The highest temperature reached 35 degrees Celsius in New York City on Monday as a result of a prolonged heat wave. (Xinhua/Wang Ying via Getty Images)
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For residents that live farther inland and want to escape the scorching heat, June gloom exists as an option to beat the heat and escape to the much cooler beaches. Once the clouds burn off during the afternoon, temperatures typically still get high enough (into the 60s and 70s) to enjoy the beach.

The marine layer helps to greatly moderate the climate along the coastline of Southern California. The average high in Los Angeles during the month of June remains within a couple of degrees of 70, and the average low hovers around 60.

About 50 miles farther inland, the average high in Riverside reaches the lower 90s by month's end with lows in the upper 50s.

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Severe spring weather across the U.S. in 2018
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Severe spring weather across the U.S. in 2018
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PHILADELPHIA, PA - MAY 12: Members of the Philadelphia Phillies ground crew roll out the tarp to cover the field due to an incoming storm before the start of a game between the Philadelphia Phillies and the New York Mets at Citizens Bank Park on May 12, 2018 in Philadelphia, Pennsylvania. (Photo by Hunter Martin/Getty Images)
HOBOKEN, NJ - MAY 10: Lightning strikes New York City next to Hudson Yards on May 10, 2018 as seen from Hoboken, New Jersey. (Photo by Gary Hershorn/Getty Images)
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