SAN FRANCISCO (KRON) -- As the Bay Area swelters under a heat wave, a spare the air alert has been extended through Wednesday, the Bay Area Air Quality Management District announced Tuesday. The alert, which was issued for smog, remains in effect for Tuesday. San Francisco temperatures expected to hit mid-90s Tuesday The BAAQMD is warning of unhealthy air quality for the early part of this week. Elevated inland temperatures, weak offshore winds, and motor vehicle exhaust are expected to create elevated concentrations of ozone or smog. The BAAQMD issues spare the air alerts when ozone pollution is forecast to reach unhealthy levels. Ozone, according to the agency, can cause throat irritation, congestion and chest pain. It can also trigger asthma, inflame the lining of the lungs and worsen bronchitis and emphysema.