The first major heat wave of the year is expected to impact the Bay Area starting Tuesday afternoon.
Most of the Bay Area and neighboring counties are under National Weather Service-issued heat advisories or excessive heat warnings, as temperatures are expected to top 110 degrees inland and the mid 90s in some coastal areas through next Tuesday.
The Weather Service has issued two heat advisories for the Bay Area — the first is from 11 a.m. Tuesday through 7 p.m. Wednesday for San Francisco, which can expect highs in the 80s and 90s.
A heat advisory has also been issued from 11 a.m. Tuesday to 8 p.m. Saturday for the San Francisco Bay shoreline, northern Monterey Bay, northern Salinas Valley, Hollister Valley and Carmel Valley. In these areas, highs will also range from the 80s to 90s.
Excessive heat warnings have also been issued for some areas, meaning temperatures are likely to be 100 degrees or higher for two or more days.
An excessive heat warning is in place from 11 a.m. Tuesday to 8 p.m. next Tuesday for the Marin and Sonoma coastal ranges, North Bay interior mountains and valleys, the Santa Cruz mountains, Santa Clara Valley, eastern Santa Clara hills, East Bay hills, southern Salinas Valley, Santa Lucia Mountains, Los Padres National Forest, San Benito Mountains and interior Monterey County. Highs between the upper 90s and 110 degrees are expected.
An excessive heat warning is also in effect from 11 a.m. Tuesday to 8 p.m. next Tuesday for the Carquinez Strait, the Sacramento-San Joaquin River Delta, Fairfield, Suisun City, Grass Valley and Stockton. These areas may experience temperatures between 105 and 115 degrees during the day.
‘Unhealthy’ air in the Bay
Bay Area air will be unhealthy Tuesday, said the Bay Area Air Quality Management District, which issued a Spare the Air Alert for smog.
The district said very high inland temperatures in the 100s and a weak afternoon sea breeze, along with motor vehicle exhaust, will create elevated concentrations of ozone, or smog.
Ozone pollution is particularly harmful for young children, seniors and those with respiratory and heart conditions. The agency said people should exercise outdoors only in the early morning hours when ozone concentrations are lower.
Spare the Air Alerts are issued when ozone pollution is forecast to reach unhealthy levels.
Ozone can cause throat irritation, congestion and chest pain. It can trigger asthma, inflame the lining of the lungs and worsen bronchitis and emphysema.
Long-term exposure can reduce lung function.
To find out when a Spare the Air Alert is in effect, residents can register for email AirAlerts at www.sparetheair.org, call 1(800) HELP-AIR, download the Spare the Air App or connect with Spare the Air on Facebook or Twitter.
Power outage anticipated
About 12,000 PG&E customers were told to anticipate possibly losing power on Tuesday as the utility monitors weather conditions that could force an intentional shutoff for safety reasons.
PG&E also activated its emergency operations center in anticipation of a Red Flag warning issued by the National Weather Service for Monday night through Tuesday night for the Sacramento Valley and foothills.
Notices were sent to customers in eight counties, including Solano and Napa counties.
Most customers put on notice of a potential Public Safety Power Shutoff, or PSPS, are in Shasta and Tehama counties, but about 96 customers in Solano County and 9 customers in Napa County were also told to prepare.
PG&E calls a Public Safety Power Shutoff when weather conditions suggest wildfires could be imminent and pose a danger to life or property. Weather forecasts and patterns that could cause a Public Safety Power Shutoff include humidity below 30%, high temperatures and winds above 19 miles per hour or with gusts of 30-40 miles per hour.
Other examples are when the National Weather Service calls a red flag warning, or when there is excess dry fuel that has accumulated.
Breezy offshore winds and high humidity are forecast for late Monday into Tuesday. The PSPS could last into early Wednesday if it is activated.
PG&E will operate six community centers in the impacted counties where customers can pick up ice.
More information and updates are available at pge.com/pspsupdates.
Staying safe in extreme heat
During periods of extreme heat, the Weather Service recommends not leaving people or pets in vehicles, limiting outdoor activities during the afternoon and evening, and staying hydrated or taking cooling breaks.
Many people will be celebrating the Fourth of July and Independence Day weekend, which may result in more people putting themselves in risky situations outside.
The Weather Service offers an extensive list and tips about staying safe during a heat wave, at weather.gov/safety/heat-during.
The heat wave can also impact pets and tips on keeping pets safe and healthy during hot weather are available from the American Society for the Prevention of Cruelty to Animals at aspca.org.
Cooling centers are also open throughout the Bay Area, with more being announced daily. A list of cooling centers is available at news.caloes.ca.gov/coolingcenters/.
The Weather Service said wildfires that develop will have the potential to spread rapidly. Erratic gusty winds may result in dangerous and unpredictable fire behavior.
A simple spark could cause a major wildfire. The community is advised to exercise extreme caution.
The Weather Service said people should avoid using barbecues or fire pits outdoors. Avoid using any source of heat or open flame outdoors.
Avoid using gas or electric power tools or mowers. Properly discard cigarettes.
Keep vehicles off dry grass or vegetation. Avoid closed areas and be alert while visiting open public lands where wildfires might occur.
Bay City News staff reporters Sarah Stierch, Tony Hicks and Thomas Hughes contributed to this report.
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