Blue skies and hot sunshine have continued into the working week after temperatures peaked at 30.2C (86.36F) in south west London at the weekend.
Overnight, it was hotter in parts of the UK than it was in Istanbul during the day.
And the Met Office has said Monday’s temperatures could soar further.
The mercury hit 24C (75C) at midnight at London City Airport – hotter than in Istanbul where temperatures stayed below 21C (70F).
In the West Midlands, working dogs at Stourbridge fire station needed to cool down.
Firefighters tweeted pictures of the dogs jumping for water from hosepipes and wrote: “@WestMidsFire even the fire dogs feeling the heat @Stourbridgefire white Watch”
In Lancashire, roads were seen melting in the high temperatures.
The Hesketh Bank and Tarleton Community Group wrote on Facebook: “If your [sic] thinking of avoiding Hesketh Lane I would think twice about using Taylors Meanygate unless you want tar all over your car. The road has melted.”
BBC Weather Watchers captured the skies at sunset on Sunday, and as Worcestershire woke to glorious blue skies on Monday.
The high temperatures have been attributed to warm air originating from the tropical Atlantic.
In some spots, the strength of the UV has been recorded as being as high as that in Cyprus and Gibraltar.
And BBC Sussex took its Big Bus Tour to seaside resort Bognor Regis.
The Met Office said the first half of the week would see temperatures in the high 20s or low 30s for many across England and Wales, but there was some cloud and drizzle to the far north of Scotland.
Temperatures are expected to return nearer to average over eastern parts of the UK on Tuesday, but the fine, very warm and sometimes humid conditions in the south will continue until Thursday.