Bay Area could see muggiest day of year; heat advisory issued

The National Weather Service issued a heat advisory for a large swath of the Bay Area on Tuesday morning that will last until 9 p.m.

Temperatures were forecast to reach the 90s across much of the North Bay, East Bay, South Bay and the Peninsula. Downtown Oakland was expected to reach the mid- to upper 80s, but the farthest east neighborhoods were expected to approach 90. San Francisco and other coastal cities were not included in the advisory, but low 80s were possible in the city's warmest neighborhoods.

"This level of heat affects most individuals sensitive to heat, especially those without effective cooling and/or adequate hydration," the weather service's advisory read. "Impacts possible in some health systems and in heat-sensitive industries."

The advisory was only in effect for one day, but strange weather by local standards was expected Tuesday night and Wednesday.

Swirling winds leftover from Tropical Storm Elida were predicted to pick up along the coast just before sunset. Muggy breezes were expected to push into the Bay Area overnight; thick fog capable of squeezing out mist and drizzle are possible in coastal areas despite temperatures in the low to mid-60s overnight, about 5 to 10 degrees warmer than a usual foggy San Francisco night. Lows were forecast to be in the mid- to upper 60s away from the coast.

Weather models predict a broad swath of the Bay Area will experience dew points in the mid-60s degrees Tuesday night into Wednesday morning, which the National Weather Service considers "sticky." The dew point could locally reach the upper 60s, which is considered "muggy" and is rare for the Bay Area. Those would be the highest dew points observed in the Bay Area so far this year, by a considerable margin. Dew point is the temperature to which air must be cooled for water vapor to condense into clouds and precipitation.

Temperatures were forecast to fall below heat advisory criteria Wednesday, though the humid air mass was expected to stick around and make for an unusually sticky day by Bay Area standards.

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