SACRAMENTO, Calif. — Election Day is almost a month away, but voting season has arrived in California.

County election officials began sending ballots Monday to millions of voters who registered to vote by mail. Monday was also the day when voters can begin casting ballots in person during business hours at their county elections office, though some were closed for Columbus Day.

Before noon, dozens of voters had cast ballots early in Orange County, said Neal Kelley, the county’s registrar of voters.

“As I’m speaking, trucks are being loaded with almost 800,000 ballots that are being mailed out,” Kelley said.

They aren’t necessarily the first Californians to vote, however. Ballots were sent last month to members of the military and people who live overseas.

The California secretary of state reported last week that nearly 18.3 million people were registered to vote as of Sept. 9. Forty-five percent are Democrats, 27 percent are Republicans and 23 percent are unaffiliated.

Citizens who want to vote have until Oct. 24 to register, and they can request a mail ballot until Nov. 1.

Alternative voting methods have been growing in popularity in recent elections. Just over half of all California ballots were cast early or by mail in the last presidential election four years ago, and the rate is expected to increase this election.

Gov. Jerry Brown last month signed legislation laying the groundwork for counties to rely even more on mail voting. SB450 allows 18 counties to set up vote centers where people can drop off ballots they’ve received by mail in the 10 days leading up to the 2018 election. In participating counties, there will be fewer vote centers than traditional neighborhood polling places.

The remaining counties can move to the system for the 2020 election if local officials choose to do so.