Health Secretary Matt Hancock has warned that everyone must stay at home this weekend - even if the sun is shining.
He spoke out after forecasters predicted a warm weekend.
Mr Hancock said: "We are set for a warm weekend in some parts of the country, but ... the disease is still spreading and we absolutely cannot afford to relax our discipline now. If we do, people will die."
And he reminded people that they had been ordered to stay at home, saying: "This advice is not a request. It is an instruction.
"Stay at home, protect lives and then you will be doing your part."
Mr Hancock, who has himself recovered from coronavirus, was speaking during the daily Downing Street press conference.
More than 2,000 critical care beds "are free and available" across the NHS and ready to use if needed, in addition to the new hospital beds to be created in dedicated Nightingale hospitals, created specially to treat coronavirus patients, he said.
The number of people with coronavirus who have died in hospital has now reached 3,605. Latest figures show there were 684 deaths in one day, the highest number so far, including 62 in the North East and Yorkshire.
The Queen is to deliver a message of encouragement to the nation on Sunday, Buckingham Palace announced.
Meanwhile, Prime Minister Boris Johnson remained in isolation in Number 11 Downing Street. It has now been seven days since he was found to have coronavirus but he continues to have symptoms.
Official advice is that people with the virus should isolate for at least seven days, and for longer if the symptoms persist.
Prince Charles, who himself has recovered from the covid-19 virus, opened the dedicated coronavirus Nightingale Hospital in London, via video link.
And NHS chief executive Sir Simon Stevens confirmed that sites in the south west of England and Yorkshire - which will have up to 1,500 beds if needed - have joined Manchester and Birmingham as the latest locations where Nightingale hospitals will be built.
