Mid-week heat wave bringing above-normal temperatures to Bay Area; heat advisory issued

A late-summer heat wave was bringing above-normal temperatures to the Bay Area and Northern California beginning Tuesday, prompting a heat advisory from the National Weather Service.

An area of high pressure is building a heat dome over the region which will last until Friday when a gradual cooling trend begins. On Tuesday, temperatures were expected to be generally be 5 to 15 degrees above normal along with widespread moderate heat risk away from the coast, the Weather Service said.

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The heat advisory was to be in effect beginning 11 a.m. Wednesday morning through 11 p.m. Thursday for the North Bay interior mountains, East Bay Hills and interior valleys, the Eastern Santa Clara Hills, Santa Cruz Mountains, Santa Lucia Mountains, San Benito Mountains, Interior Monterey County, and a wide swath of the Central Valley.

Inland locations will reach near-critical fire weather conditions Tuesday morning because of poor relative humidity recoveries and light northerly/offshore flow, the Weather Service said.

On Wednesday and Thursday, areas away from the coast will see high temperatures 10 to 20 degrees above normal and the conditions could last into Friday, including the near-critical fire weather conditions, the Weather Service said.

The high inland temperatures combined with motor vehicle exhaust also prompted the Bay Area Air Quality Management District to issue a Spare the Air Alert for Tuesday and Wednesday. The district said the ozone pollution, or smog, was forecast to reach unhealthy levels, especially for young children, seniors, and those with respiratory and heart conditions. 

During a Spare the Air Alert, outdoor exercise should be limited to the early morning hours when ozone concentrations are lower, the district said.

In:
• National Weather Service
• Heat Wave