The 42nd president is scheduled to speak sometime between 6 and 7 p.m. followed by the outgoing mayor, famed Three Tenors opera singer Placido Domingo and Garcetti.
Clinton endorsed Wendy Greuel during the mayoral campaign.
Celebrate L.A. begins at 5 p.m. and ends after 9 p.m. City officials promise surprise concerts by Grammy-winning artists, along with Spanish and Native American musical performances. Food trucks will be on hand, too.
Clinton's appearance in L.A. will be the second of the day by a U.S. president. President Obama is scheduled to stop by a fund-raiser in Santa Monica in the morning.