Coastal cool-down rolls in before summer kicks off

The Bay Area is trading its recent warm, dry spell for a cooler pattern just in time for Memorial Day. A shift in the atmosphere is pushing in cooler air from the Pacific, bringing back the familiar gray skies and ocean breezes. Instead of high pressure keeping things toasty, a low-pressure system is moving in, allowing cooler air to replace the warm air that’s been hanging around. This change means the marine layer—the layer of cool, moist air near the coast—is thickening up again. On Friday morning, it was already 1, 000 to 1, 500 feet deep, enough to blanket coastal areas in fog. Over the weekend, that fog will spread farther inland, making things feel more like early summer than late spring. Cities like San Jose, usually warmer this time of year, will start the day under cloudy skies, keeping temperatures down.The cooling isn’t just about fog. The ocean air, currently in the upper 50s, will push inland, dropping temperatures in spots that have been heating up lately. Oakland could see highs only in the mid-60s by Monday, while San Francisco stays mostly in the 60s. Even San Jose, which often sees warmer weather, will hover around 75 degrees. Areas right by the ocean won’t see much sun at all. A little extra moisture is tagging along too. Light drizzle is possible Sunday and Monday, adding to the gloomy vibe. The coolest stretch looks to peak next Tuesday before things start warming up again. Locals might call this the shift from "May gray" to "June gloom, " a yearly reminder that summer takes its time arriving in Northern California.