June Gloom
Encyclopedia
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
term for a weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
pattern that results in cloudy, overcast skies with cool temperatures during the late spring
Spring (season)
Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of the exact timing of "spring" varies according to local climate, cultures and...
and early summer
Summer
Summer is the warmest of the four temperate seasons, between spring and autumn. At the summer solstice, the days are longest and the nights are shortest, with day-length decreasing as the season progresses after the solstice...
. June Gloom in southern California is caused by the marine layer
Marine layer
A marine layer is an air mass which develops over the surface of a large body of water such as the ocean or large lake in the presence of a temperature inversion. The inversion itself is usually initiated by the cooling effect of the water on the surface layer of an otherwise warm air mass...
effect common to the West Coast, and is enhanced by the Catalina eddy
Catalina eddy
The "Catalina eddy," also called the "coastal eddy," is a localized weather phenomenon that occurs in the so-called "Bight of California", the mostly convex portion of the Southern California coast running from Point Conception to San Diego...
local to southern California. June Gloom has other colloquial names if the same weather pattern occurs in May, July, or August. The June Gloom period is usually the cloudiest time of year for coastal southern California. This weather pattern occurs in other parts of the world where climates and conditions are similar.
Phenomenon
Marine layer
A marine layer is an air mass which develops over the surface of a large body of water such as the ocean or large lake in the presence of a temperature inversion. The inversion itself is usually initiated by the cooling effect of the water on the surface layer of an otherwise warm air mass...
, move in at night, usually after midnight, and typically dissipate in the late morning, giving way to clear, sunny skies. During a heavy June Gloom season, the condition may persist into the afternoon, or even all day during an exceptionally strong event. If the air is saturated with moisture, fog
Fog
Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...
also may develop with June Gloom. Early mornings during June Gloom are typically foggy, with frequent light mist
Mist
Mist is a phenomenon of small droplets suspended in air. It can occur as part of natural weather or volcanic activity, and is common in cold air above warmer water, in exhaled air in the cold, and in a steam room of a sauna. It can also be created artificially with aerosol canisters if the...
and occasional drizzle
Drizzle
Drizzle is a light rain precipitation consisting of liquid water drops smaller than those of rain, and generally smaller than 0.5 mm in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates due to drizzle are on the order of a millimetre...
. Fog and drizzle normally are found near the furthest inland extent of the gloom, where the cloud deck is closest to the ground. The fog recedes and reveals low clouds by mid-to-late morning; by late morning to early afternoon, solar heating usually is sufficient to evaporate the clouds altogether. The phenomenon forms earliest and lasts longest at the coast, with later formation and earlier dissipation in areas further inland. When the marine layer is strong and deep, clouds can fill the Los Angeles Basin
Los Angeles Basin
The Los Angeles Basin is the coastal sediment-filled plain located between the Peninsular and Transverse ranges in southern California in the United States containing the central part of the city of Los Angeles as well as its southern and southeastern suburbs...
and spill over into the San Fernando Valley
San Fernando Valley
The San Fernando Valley is an urbanized valley located in the Los Angeles metropolitan area of southern California, United States, defined by the dramatic mountains of the Transverse Ranges circling it...
and San Gabriel Valley
San Gabriel Valley
The San Gabriel Valley is one of the principal valleys of Southern California, United States. It lies to the east of Los Angeles, to the north of the Puente Hills, to the south of the San Gabriel Mountains, and west of the Inland Empire. It derives its name from the San Gabriel River that flows...
, even extending into the Santa Clarita Valley
Santa Clarita Valley
The Santa Clarita Valley is the valley of the Santa Clara River in Southern California. It stretches through Los Angeles County and Ventura County. Its main population center is the city of Santa Clarita. The valley was part of the Rancho San Francisco Mexican land grant...
on exceptionally strong June Gloom mornings. If the condition is not as strong, the Basin may be filled while the valleys may be clear. It is not uncommon for motorists to drive over the Sepulveda Pass
Sepulveda Pass
Sepulveda Pass is a mountain pass through the Santa Monica Mountains in Los Angeles.It connects the Los Angeles Basin to the San Fernando Valley via the San Diego Freeway and Sepulveda Boulevard and experiences heavy traffic on a regular basis, commonly experiencing major traffic slowdowns and...
from the clear, sunny San Fernando Valley
San Fernando Valley
The San Fernando Valley is an urbanized valley located in the Los Angeles metropolitan area of southern California, United States, defined by the dramatic mountains of the Transverse Ranges circling it...
and plunge into a cloudy, fog-filled Los Angeles. On a weak June Gloom morning, the clouds and fog may only be present within a mile or two of the coastline, affecting only the beach cities.
June Gloom has other names in southern California if it occurs in other months. These include May Gray if it begins early, and No-sky July or Fogust if it continues past June. In the early 20th century, this phenomenon was sometimes known as the high fog. A long June Gloom season, extending late into the summer, is known as Summer Bummer. The negative effects of a long June Gloom on the coastal California tourism industry is often reported in the local news media.
When June Gloom occurs in a given year, it is usually the cloudiest period of the year in contrast to the remainder of southern California's typically sunny climate. For example, June is on average the cloudiest month of the year in San Diego. The number of days in May and June that are "gloomy" vary from year to year. Years with warmer ocean temperatures, referred to as El Niño
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...
, may result in fewer gray days in May and June. Cooler ocean temperatures, associated with La Niña
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...
, usually foretell a more gray period.
June Gloom has been reported by some Californians to bring on symptoms consistent with seasonal affective disorder
Seasonal affective disorder
Seasonal affective disorder , also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn...
, however, the normally-very-sunny Los Angeles climate also is home to people who thrive during the brief seasonal respite the gloom provides from the unending sunshine and clear skies.
Northern California
Northern and Central California coastal areas typically have foggy weather all throughout the summer into early fall.Pacific Northwest
A similar phenomenon can occur in the Pacific NorthwestPacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
between May and early July, though the phrase "June Gloom" is not nearly as commonly heard as it is in California due to the frequency of cloudy or overcast weather throughout the year in the Pacific Northwest. As locations east of the Cascade Mountains rapidly heat up in late spring, the resultant pressure gradient pulls cool marine air onshore, over the coastal mountains, and into the Willamette Valley of Oregon, as well as the non-coastal parts of southwestern Washington. At night the already cool and moist marine layer becomes even cooler, fueling the formation of low clouds. During late spring and early summer, it is quite common for cities like Portland to be completely overcast in the morning and remain as such until early afternoon, at which time the clouds dissipate and the sky becomes mostly clear.
As summer progresses, the marine layer typically gets shallower and has some difficulty crossing the Coast Range. While stratus cloud decks can occasionally reach the interior valleys in July and August, they are very often confined to the coastline during this time.
Elsewhere in the World
The condition is prevalent in many parts of the world where an offshore marine layerMarine layer
A marine layer is an air mass which develops over the surface of a large body of water such as the ocean or large lake in the presence of a temperature inversion. The inversion itself is usually initiated by the cooling effect of the water on the surface layer of an otherwise warm air mass...
of stratus
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
or stratocumulus clouds is common, such as the western coasts of continents—particularly off Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
, Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
, Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
, atlantic Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
and Northern California
Northern California
Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...
, particularly San Francisco. Such cloud systems are persistent year-round off the coast; in certain seasons they move ashore and create the cloudy, cool effect on land. These places typically are located in a Mediterranean climate
Mediterranean climate
A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin, and is a particular variety of subtropical climate...
(Köppen climate classification
Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by Crimea German climatologist Wladimir Köppen in 1884, with several later modifications by Köppen himself, notably in 1918 and 1936...
Csa), but the effect occurs in other climate zones as well, where conditions are favorable.