Sunday will be the hot, sunny, and smoggy, according to the National Weather Service.  High temperatures on Sunday will range from the low 80s in Oakland and San Francisco to 99 in San Jose and 101 in Livermore, forecasters say.

The Weather Service has issued a heat advisory from 12 p.m. to 9 p.m. Sunday.

"A heat advisory means that a period of hot temperatures is expected. This heat advisory is primarily targeted at the elderly and very young and the infirm -- those who might be more sensitive to heat and thus at greater risk," the advisory explains.

"People who fall into this category should be especially careful by drinking plenty of water and seeking a cool location during the day if no air conditioning is available where you live."

"Wear lightweight, light-colored, loose-fitting clothing. Wear a hat to shield yourself from the sun," the Weather Service advises. "Do not leave young children and pets in vehicles under any circumstances."

Monday should be a bit cooler, with patchy fog along the coast.

The Bay Area Air Quality Management District also issued a "Spare the Air" health alert for Sunday, which advises residents to reduce their energy use during periods of increased pollution.

The warning, the second issued for smog this year, means that the air will contain high concentrations of ozone.

"Air quality is expected to be unhealthy over the Fourth of July holiday weekend," said Jack Broadbent, executive officer of the air quality district. "It's important that we reduce the number of cars on Bay Area roads every day to prevent unhealthy air."

High ozone levels are produced when motor vehicle exhaust, gasoline vapors, industrial emissions and household chemicals combine with oxygen in the presence of heat and sunlight. Ozone can irritate the throat and lungs, trigger asthma and worsen bronchitis and emphysema, among other hazards.

Residents are encouraged to drive less and reduce their energy use to help lower pollution levels during the alert period. Children, seniors and those with respiratory and heart conditions should limit vigorous outdoor exercise to the early morning hours when ozone concentrations are lower.

Residents should also avoid using gas-powered lawn mowers and leaf blowers, avoid the use of aerosol spray cleaners, paints and hairspray, and cook indoors rather than on the barbecue.