SAN FRANCISCO (KRON) -- Below-average temperatures, drizzly fog, and a chance of rain showers are forecast around the San Francisco Bay Area this week. KRON4 Meteorologist Dave Spahr said on Monday, "The first of two systems has arrived. A few early spotty showers -- mostly SF down through the Peninsula and parts of the South Bay -- will clear out by the afternoon." Cool temperatures will continue into the middle of the week, according to the National Weather Service Bay Area. After a cloudy Tuesday, a second system is forecast to arrive early Wednesday morning. "Another round of showers possible. This looks a touch more robust, but watching for possible lightning. Rainfall will be very scattered and modest," Spahr said. "This is such an unusual pattern this time of year," KRON4 Meteorologist Kyla Grogan said. Rainfall totals will only be in the hundredths of an inch, according to NWS. Lunar eclipse, supermoon will happen at same time Tuesday night Damp and cool weather will disappear on Thursday as mostly sunny skies return. A weekend warmup will see temperatures rising into the high 80s and low 90s. "A quick warming trend to finish the week and returning to hot come the weekend," Spahr said. Sunday marks the first day of fall.