June Gloom - Phenomenon

Phenomenon

A typical June Gloom day consists of marine stratus clouds covering the coast of southern California, extending a varying distance inland depending on the strength of the June Gloom effect each day. The fog and clouds, which are formed by the marine layer, 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 also may develop with June Gloom. Early mornings during June Gloom are typically foggy, with frequent light mist and occasional drizzle. 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 and spill over into the San Fernando Valley and San Gabriel Valley, even extending into the Santa Clarita Valley 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 from the clear, sunny San Fernando Valley 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.

The months of May and June are typically the cloudiest months of the year in coastal southern California, having only 59% and 58% sunny days, respectively, on average. The number of days in May and June that are "gloomy" vary from year to year. Anomalies in sea surface temperature can be used to forecast the number and intensity of June Gloom days. Years with warmer ocean temperatures, referred to as El Niño, may result in fewer gray days in May and June. Cooler ocean temperatures, associated with La Niña, usually foretell a more gray period.

June Gloom has been reported by some Californians to bring on symptoms consistent with seasonal affective disorder, although this is not well-supported by evidence. 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.

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. The phenomenon can be especially disorienting to visitors from inland areas who, coming from the summer heat, would not expect cool temperatures and clouds and fog at the beach.