Police face “one of their biggest challenges” of the lockdown this weekend as sunny weather risks drawing crowds to parks and beauty spots.
Devon and Cornwall Police Chief Constable Shaun Sawyer told the BBC it was a “pivotal weekend”, urging people to “play their part” and avoid travel.
Ministers have said “stay at home” is an instruction, not a request.
Senior medics urged people to avoid travel for the sake of two nurses who died of coronavirus.
A forecast of warm weather across much of the UK this weekend has led to warnings from local councils, tourism bosses and police urging people to stay away from coastal areas, national parks and other visitor destinations.
Restrictions state that everybody must stay at home where possible, and only leave if they have a “reasonable excuse”, such as exercise or shopping for basic necessities.
Prof Neil Ferguson, a leading scientist advising the government, has warned the coronavirus infection rate in the UK could remain high for “weeks and weeks” if people ignore social distancing rules this weekend.
The latest figures showed 3,605 people with the virus have now died in the UK, with 684 deaths recorded on Friday. There are 38,168 confirmed cases.