The coronavirus pandemic is raging in Florida as the state reports more than 10,000 new infections for a sixth day in a row, but California's cases and hospitalisations are beginning to stabilise after a surge.
Florida has become the epicentre of the latest COVID-19 surge, prompting the state's teachers union to sue Republican Governor Ron DeSantis over his plan to reopen schools for in-class instruction.
In California, which emerged as another coronavirus hotspot in July, Governor Gavin Newsom said new infections, hospitalisations and intensive care unit admissions were all still rising in the nation's most populous state but not nearly at the pace of recent weeks.
"We are seeing a reduction in the rate of growth but a rate of growth nonetheless," Newsom, a Democrat, said at a briefing in Sacramento on Monday.
"Hospitalisations and ICU (admissions) continue to be cause of concern in this state. That's why we want everybody to double down on what we've been doing," the governor said.
Teams from the Federal Emergency Management Agency arrived to pitch in at strapped Southern California hospitals.
"We really pushed up last week to our limits. If we had continued to see accelerating number of cases coming into the hospital, something would have to give," said Dr. Allan Williamson, chief medical officer at Eisenhower Medical Centre in Rancho Mirage, east of Los Angeles.
The mayor of Los Angeles, Eric Garcetti, has more than once threatened to impose a new "stay-at-home" order in America's second-largest city if trends were not reversed.
Florida reported 10,347 new infections on Monday, the sixth day in a row the state has announced over 10,000 new cases. Another 92 people died in Florida, increasing the state's death toll to 5183.
DeSantis, who has been sharply criticised for his handling of the crisis, said over the weekend that positivity rates and COVID-19-related emergency room visits have been trending lower in recent weeks.
New York, which has recorded far more deaths than any other US state, 32,000, recorded only eight fatalities on Sunday.
The total number of people hospitalised in New York for the disease fell to 716, the fewest since March 18, Governor Andrew Cuomo said. Restrictions were eased slightly with zoos and the Statue of Liberty reopening as well as professional sports without fans.
Chicago Mayor Lori Lightfoot, a Democrat, imposed new clamp-downs, including a ban on indoor service at bars and shutdown of personal services such as shaves and facials that require the removal of masks.
"While we aren't near the peak of the pandemic from earlier this year, none of us wants to go back there," Lightfoot said in a statement.
Metrics nationwide show a continued surge in the pandemic, with 32 states reporting record increases in COVID-19 cases in July and 15 states reporting record increases in deaths.
The illness has killed 140,000 people in the US and infected some 3.7 million, both figures leading the world.
President Donald Trump, who had pushed back on mask requirements by state and local officials, on Monday posted a black and white photo of himself wearing one on Twitter.
"We are United in our effort to defeat the Invisible China Virus, and many people say that it is Patriotic to wear a face mask when you can't socially distance. There is nobody more Patriotic than me, your favorite President!," Trump said in a tweet.