Elec. Code, § 10735

(a) (1) In the case of a special election due to a catastrophe that causes a vacancy in at least 101 offices of the United States House of Representatives, the county elections official shall, to the greatest extent practicable, deliver vote by mail ballots requested pursuant to Chapter 2 (commencing with Section 3101) of Division 3 not later than 15 days after the date on which the Speaker of the United States House of Representatives announces the vacancy.

(2) In the case of a special election due to a catastrophe that causes a vacancy in at least one-fourth of the total offices of the United States House of Representatives representing California but not a vacancy in at least 101 of the offices of the United States House of Representatives, the county elections official shall, to the greatest extent practicable, deliver vote by mail ballots requested pursuant to Chapter 2 (commencing with Section 3101) of Division 3 not later than 15 days after the date on which the Governor issues the proclamation calling the election to fill the vacancy.

(b) A vote by mail ballot cast pursuant to Chapter 2 (commencing with Section 3101) of Division 3 in a special general election conducted pursuant to this chapter shall be postmarked not later than the date of the election, shall be received by the county elections official not later than 45 days after the date on which the elections official transmitted the ballot to the voter, and shall comply with all other relevant requirements of this code.

(c) Notwithstanding any other provision of law, any deadlines relating to canvassing, announcement of election results, or certification of election results may be extended for a reasonable period of time to facilitate the tabulating and processing of ballots cast pursuant to Chapter 2 (commencing with Section 3101) of Division 3. An extension of a deadline pursuant to this section must be authorized by the Secretary of State.