Unsurpassed traffic levels are expected as people switch the city to popular beaches and beauty sites.
Many parts of the country are heading for a heat wave with temperatures set to reach 32 degrees, the Met Office said.
Half of drivers plan their escape by car, and roads turn, according to reports.
The M5 stood still this afternoon as the British went out on their weekend stay against Devon and Cornwall, according to The Sun.
Beachgoers are already flocking to the sea in Brighton, while more than 150,000 people are expected to visit Bournemouth and Dorset this weekend amid highs of 26 degrees.
It is estimated that 97 percent of a total of 16,000 hotel rooms and 30,000 beds have already been reserved for Saturday in the city.
Tim Seward, president of the Bournemouth Area Hospitality Association, said the increase was due to increased demand caused by overseas travel restrictions.
“Every summer day when the sun is shining will obviously be busy,” he said.
But this year, demand has been captured because people cannot travel abroad.
He added: “We expect the hotels to be fully booked by Saturday.”
Those pulling the heat in London can expect altitudes of 31 degrees, higher than Ibiza predicted 29 degrees on Sunday.
Super Sun Weekend
Extreme heat warnings have been issued by both medical authorities and veterinarians urging people to protect the vulnerable and the animals.
Even areas further north including Hull and Newcastle are expected to reach the mid to high 20s as the weekend progresses with temperatures “building day-to-day”, according to the Met Office.
The criteria for an official heat wave are three days with persistently high temperatures, but this can vary across the country.
Met Office meteorologist Andy Page said: “The widening of the Azores highs is the main reason for the UK’s current weather pattern, which will see much of the UK reach heatwave thresholds over the weekend and into early next week.
“High temperatures remain in the forecast well into next week, but there is a risk of isolated heavy showers in the south of Britain on Monday and Tuesday, although it should be fine in most areas.”
A heat-health warning was issued by Public Health England (PHE) ahead of expected extreme temperatures.
PHE advised people to keep an eye out for those who may be struggling to stay cool and hydrated, such as the elderly and those living alone.
It follows a week-long flood in south-east England that is causing transport disruptions in London.