Gray, Gloom Give Way to Gorgeous in July

May gray. June gloom. Nearly all Southern California coastal residents have heard these words used to describe the overcast conditions that lead into summer.

The gray skies, chilly waters and cooler air temperatures tend to give way to ideal beach conditions in early July, when the relationship between the ocean water and air temperature causes a shift from dreary to sunny weather.

“'June gloom' is simply the street term to describe our cold marine layer where the ocean hasn’t quite warmed up,” said Mark Jackson, a meteorologist with the National Weather Service. “Our ocean temperatures are cool, and then we get warm air on top of that. A moist, cool flow comes off the ocean, and when you have warmer air on top of that, you get clouds and fog.”

Research from UC San Diego’s California Nevada Applications Program and the California Climate Change Center further explains that the “formation of these [marine layer] clouds usually begins when wind over the water surface mixes moist surface air upwards. As this air moves up, it expands and cools. The cooling causes the relative humidity to increase and once the relative humidity reaches 100 percent, clouds begin to form.”

Those two variables change with the seasons, and a high-pressure weather system mixed with a lack of cool coastal breezes off the ocean causes June gloom to give way to sunny skies and warmer waters.

“For the most part, when we have low pressure to the north, we get that wind that comes off the water that’s cool and moist, and typically we’ll have overnight clouds and fog and then the sun comes up and the land heats up,” Jackson said.

Due to Southern California’s location, the pairing of cool waters and warm air leading to clouds happens for two months—May and June—with less than 50 percent of average sunshine occurring each month, according to the California Climate Change Center and California Nevada Applications Program.

While warmer waters in early July may make taking a swim in the ocean more desirable, it doesn’t result in big waves for surfers.

“The surf tends to be smaller in the spring and the summer," said Vince Ray, director of the Hermosa Beach Chevron Surf Camp. "Sometimes in the spring it can be choppier because it’s windier. Generally summer is calmer; less wind, smaller waves, and warmer water.

“The surf gets bigger and more consistent in October or November, and the water gets cool. For experts, the best time to surf would be from October to March,” Ray said.

Global warming has long been cited as the cause for less than ideal weather conditions, but Jackson disputed such broad assertions.

“People have a tendency to look at our climate and make statements like, ‘We’re warm right now, it must be global warming,'” Jackson said. “The proper term is climate change. Our global temperatures have increased, but they are small increases over the last 100 years.”

Now warm temperatures along the coast are trending, but Jackson said he couldn’t say if any temperature records would be broken along the coast or further inland.

“It’s just a matter of how these waves and troughs and high-pressure systems kind of fluctuate around. Right now we have a strong high-pressure system that extends over most of the Western two-thirds of the country,” Jackson said. “Since we really don’t have much of a flow off of the ocean right now, it keeps a lot of the cold air off the shoreline. … We’re missing that cold, moist air being shoved on land.”