We're looking at temperatures in the mid-90s Wednesday for parts of San Francisco, with 80 degrees predicted at the beach, in the official kickoff of the city's true summer season.Just as the rest of the country is starting to put away their summer clothes and close up their summer houses for the se ason, San Francisco is kicking off its real-deal summer with a mini-heatwave. Things hopefully cool off again by Thursday so we don't bake too much, but the Chronicle says that today's very warm and sunny preview will be just the first taste, with Wednesday even hotter.Gone will be the usual sea breeze, perhaps even at the coast, and they're forecasting a 95-degree high in the Mission District Wednesday afternoon, with 93 in the Castro, 92 in Pacific Heights, and 80 in the Outer Sunset and at Ocean Beach.These highs aren't totally guaranteed, thanks to the unsettled bands of moisture coming at us from the south, complete with high clouds, some of which gave Los Angeles some surprise downpours and lightning on Tuesday morning. Those high clouds will trap some of the heat at night, as the Chronicle meteorology team explains, keeping things warm on Wednesday night, but depending on the cloud cover during the day this could also bring the high temps down.So far this year, we had that one extended heatwave in March, where temperatures toyed with records in the mid-80s. And the last time SF got into the upper 90s was a 97-degree high on October 6, 2024, which followed a weeklong heatwave that forecasters actually didn't see coming — and that left many miserable, especially if they had no air conditioning.The ocean breeze and lower temps are forecast to return on Thursday, with a high in the city around 75 degrees.AccuWeather has San Francisco forecast to see highs of around 69 or 70 all the way from the weekend through next week, but we'll see if that changes.Areas of high pressure that interrupt the usual onshore breeze that keeps San Francisco cool are typical at this time of year and through October, but the crazy El Nino season brewing in the Pacific could upend that pattern and send early rain our way this year. Buckle up. ...read more read less