Eighteen government websites designed by a Florida company to deliver voters polling information and election results repeatedly crashed Tuesday.
The high web traffic overwhelmed a company server, said Maureen Szlemp, who added that technicians were working to restore access to the sites.
She said the company had not experienced outages like this before.
Some sites, including Contra Costa County's, have come back, while others are still down.
Ventura County officials are telling voters to use their mobile phone app "VC elections" for updates.
The Ventura site has been going down and coming back since 8 a.m. Tuesday, said Tracy Saucedo, assistant registrar of voters.
"At first they said wait 30 minutes and then that turned into, 'We are not so sure anymore,'" she said Tuesday afternoon.
Voters resorted to older methods and called the registrar for information, she said.
"It was kind of old school," she said.