Bay Area residents can expect one last day of sweltering heat before a major cooldown commences. The National Weather Service (NWS) San Francisco Bay Area reports that the warm temperatures will persist through Monday, with the interior possibly reaching up to the mid-90s and the coast seeing a range from the 60s to mid-70s.

As we move into Tuesday, we anticipate a cooling trend "in response to an upper level trough approaching and moving across the region mid-to-late week", according to the NWS BayArea. This means lower temperatures are on the horizon, with the possibility of even falling below seasonal averages as the trough takes effect. Winds are also expected to pick up, reaching 20-30 mph in certain areas.

The cooling trend is expected to commence tonight as "more widespread clouds to penetrate inland into the coastal adjacent valleys as the marine layer begins to deepen", per the National Weather Service forecast. Tonight’s lows will dip into the upper 40s in colder spots, and the mid-50s in others. Coastal stratus is likely to return following its retreat, but the timing specifics are uncertain, as recently released TAFs suggest.

Looking ahead to the rest of the week, the NWS forecast predicts that the upper-level trough will bring temperatures back to near or below seasonal averages, with the mid-70s to mid-80s across the interior and more widespread 60s at the coast. Winds will continue to gradually strengthen on Tuesday, in part preparing to usher in a second upper-level disturbance expected next weekend. Meanwhile, coastal mariners must remain vigilant as patchy dense fog, particularly around Monterey Bay, may rapidly reduce visibility early Monday morning before it begins to clear towards mid to late morning.