The storm's maximum sustained winds reached 210 kilometers (130 miles) per hour and was in a stationary position some 675 kilometers (420 miles) southwest of Zihuatanejo, Guerrero state, according to the US National Hurricane Center.
Blanca became a category four hurricane, the second most powerful on the five-level Saffir-Simpson scale.
The center's tracking map shows Blanca striking the southwestern coast of the Baja California peninsula as a tropical storm on Sunday, the same day that Mexicans vote in congressional and municipal elections.
Authorities in Los Cabos said they were monitoring the storm's progress.