A new record temperature has been set for 2019, with the mercury expected to keep rising.
The Met Office said a reading of 30.8C (87.4F) was taken in Charlwood, Surrey, on Saturday morning, with temperatures expected to rise as high as 34C (93.2F) later in the day.
This would fall just short of the 35.6C (96F) June record set in 1976.
It will be hottest across the south, into the Midlands and as far north as Lincolnshire.
Friday’s reading of 30C (86F) at Achnagart in Scotland was the previous record for this year.
Glastonbury festival-goers will be treated to sunny and dry 31C (87.8F) conditions on Saturday afternoon.
The highest temperature ever recorded at the music festival was 31.2C (88F) in 2017.
Sales of barbecue food have soared, according to Tesco, with the supermarket predicting it will sell more than one million packs of sausages, 650,000 packs of burgers and 50,000 disposable barbecues over the weekend.
The predicted figure for sales of barbecue meat is double that of last weekend.
As people flocked to the seaside to make the most of the weather, the M5 was closed in both directions in Somerset because of problems with overhead power cables.
England’s most senior nurse called on the public to help children, the elderly and other vulnerable people at risk of being affected by the heat.
Ruth May, Chief Nursing Officer for England, said: “Like lots of people I’m looking forward to having fun in the sun with family and friends this weekend, but nobody wants to spend a pleasant day stuck in a hospital or urgent treatment centre.
— Met Office (@metoffice) June 29, 2019
“So, whether you’re going to be out in the garden like me or heading off to Glastonbury, it’s really important to take simple precautions like drinking plenty of water, using high-factor sunscreen and remembering to take allergy medication if you need it – as is making sure to check in on neighbours and loved ones who can suffer the most from heat and pollen.”
According to NHS England, almost 3,000 people were admitted to hospital because of heat-related ailments in 2017/18, including 632 with severe sunburn, 100 cases of heat exhaustion and 223 cases of sun and heat-stroke.
NHS England and emergency services have issued warnings to the public to take care in the hot conditions.
It follows the death of 12-year-old Shukri Yahya Abdi, who drowned in the River Irwell in Bury on Thursday.
Several European countries have reported record temperatures this week, including France which hit an all-time heat record of 44.3C (111F) on Friday.
While people in southern areas enjoy the sunshine and warmth, conditions will be considerably cooler and stormier in the north, where a cold weather front is moving in.
For Saturday the Met Office has issued a severe weather warning for lightning across areas in Northern Ireland and western Scotland, while a severe weather warning for thunderstorms spans the north-east of England and the south-east of Scotland.
Despite this, pollen counts and UV levels will be high or very high everywhere except in northern Scotland, according to the forecaster.