California's governor has imposed a curfew on social gatherings and other non-essential activities in one of the most intrusive of the restrictions being ordered across the country to curb an alarming surge in novel coronavirus infections.
The stay-at-home order will go into effect from 10pm until 5am each day, starting on Saturday and ending on December 21, covering 41 of California's 58 counties.
"The virus is spreading at a pace we haven't seen since the start of this pandemic, and the next several days and weeks will be critical to stop the surge," Governor Gavin Newsom, a Democrat, announced a week before the Thanksgiving holiday.
A similar curfew order was issued on Thursday in Ohio and will remain in effect for the next 21 days, Governor Mike DeWine, a Republican, announced separately.
In California, the restriction essentially marks a return to the first-in-the-nation, statewide stay-home order that Newsom imposed in March, except this time it does not apply around the clock.
Signs of a resurgent public health crisis have emerged more starkly across the country, with officials forced to retreat from tentative steps to normalise daily life.
The US Centers for Disease Control and Prevention issued a "strong recommendation" on Thursday that Americans not travel for the holiday.
Later in the day, President-elect Joe Biden emerged from a teleconference with 10 governors saying they had discussed a possible universal face-mask requirement - which Biden has strenuously advocated as a "patriotic duty".
Newsom and DeWine's orders are among the most restrictive of measures state and local government leaders nationwide have imposed on life this week as COVID-19 hospitalisations and deaths soar heading into the winter.
The number of US patients hospitalised with COVID-19 has jumped nearly 50 per cent in the past two weeks to more than 80,000 people, a Reuters tally shows, the most at any time during the pandemic.
The US death toll from COVID-19 surpassed 250,000 on Wednesday, with more than 2000 additional lives lost as of Thursday, with the cumulative number projected to climb well above 400,000 by March.