From an Alameda County press release:
The Alameda County Registrar of Voters will be open Saturday and Sunday, June 2 and 3, to allow voters to vote early for the June 5 Presidential Primary Election. Alameda County voters may come to the Registrar of Voters office between 10 a.m. and 3 p.m. on Saturday or Sunday to vote. The office is currently open for voting Monday through Friday, from 8:30 a.m. to 5 p.m. The Registrar’s office also will be open on Election Day, Tuesday, June 5, from 7 a.m. to 8 p.m.
The Registrar of Voters office is located in the basement of the Rene C. Davidson Alameda County Courthouse at 1225 Fallon St., Oakland. Voters wishing to cast ballots during weekend hours will be able to access the Registrar of Voters office through the12th Street entrance of the Courthouse.
For more information about early voting, call the Registrar of Voters office at (510) 272-6973.