"Sunny" San Diego did not have one clear day in May, according to data from the National Weather Service, and it appears June will trend gloomy as well.
During the month known by locals for its gray, San Diego had 10 days without sunshine and 8 days with partial clouds (which are ranked an 8 out of 10 cloudiness level), according to National Weather Service meteorologist Alex Tardy, a meteorologist with the National Weather Service San Diego. Even the days considered "clear" by the NWS metrics had at least some cloud cover.
San Diego News
The number of cloudy days this year is "much above average" for San Diego, which typically has about 58% cloud cover for the month. This year, the average sky cover was 82%.
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Fox Weather reported San Diego, known for its beaches and sunshine, was one of the cloudiest locales in the continental U.S. last month. The only place with more cloud cover was a remote city in Alaska but the 5,000 residents and natives of Utqiagvik may be more accustomed to sunless days. This year, their first glimpse of sunshine came 65 days into the new year.
The cloud cover develops when surface water temperatures along the west coast are much cooler than the air temperature. The air in contact with the water cools to the point clouds form, the NWS said. This can occur near any large body of water but here in SoCal, we refer to the phenomenon as "May Gray" and "June Gloom."
“May and June, these are the months in San Diego County where we typically see the most marine layer and the least amount of sun, so that’s what you’re looking here, percent of sunshine is going to be the lowest on average for the months of May and June," NBC 7 Meteorologist Sheena Parveen said.
So far for the first week of June, San Diego continues to be socked in by that marine layer, Parveen said.
Another contributing factor to the higher-than-average cloud cover this year is an active winter weather season, according to Tardy, which has created an anomaly between the cold Pacific and warm weather systems over Canada and caused a deep marine layer to expand and lift.
Without much sunshine, San Diego's temperatures have been cooler than average as well. Tardy said temperatures were about 2.3 degrees cooler than the 30-year average.
