In June 1987, I was living in San Francisco and was to attend a conference for work in Northridge. Thrilled at getting out of the fog, I packed shorts, tanks tops and a bathing suit - the hotel had an outdoor pool - and got ready for some heat. I arrived in Northridge to find all the Southern Californians wearing sweatshirts, and the weather quite similar to what I had left at home. "June gloom", they all said, "Didn't you know?"
The weather phenomena called June gloom is, according to Wikipedia, "a California term for a weather pattern that results in overcast skies with mild temperatures during the late spring and early summer. The condition is prevalent in many parts of the world where marine stratus or stratocumulus clouds are common, particularly off the western coasts of continents..."
I just arrived back in Southern California four days ago, and even though it is still late May, June gloom is in force. Some days it has burned off in the afternoon, some days it lasts all day. I put on my sweatshirt with no complaints. There'll be plenty of heat later on. Right now, I like it. It reminds me of San Francisco.