A heatwave record set 31 years ago could be equalled today - and broken early next week.
There have been 33 days so far this year when temperatures have exceeded 30C (86F) somewhere in the UK.
That is just one day short of the 34 days recorded back in 1995 - with 33C (91F) forecast in southern areas on Sunday.
Temperatures are also expected to soar on Tuesday, Wednesday and Thursday, meaning another meteorological record will be set.
Met Office data shows Saturday narrowly missed exceeding this 30C threshold, with highs of 29.8C (85.6F) recorded in Hull.
This summer's extreme weather has been linked to a period of "historic and unprecedented change" to the UK's climate, with multiple records broken.
Both May and June broke the Met Office's monthly temperature records for the UK, while July was the driest on record.
Meanwhile, record-low rainfall means the whole of Wales and half of England have now been plunged into drought.
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The UK Health Security Agency has also warned Britain is on track for the highest number of heat-associated deaths in history.
Yellow heat health alerts are in force until 9pm on Thursday.
Sky News meteorologist Chris England said: "Temperatures are climbing again, with heatwave thresholds likely to be exceeded for an unprecedented fifth time this year.
"England looks hottest, with 36C (97F) possible on Wednesday and Thursday, with Wales only a little behind, but there's a chance all four nations may go over the limits."
Because of how heatwaves are recorded, he said recent conditions "could well be described as part of a prolonged heatwave interspersed with a few brief cooler interludes".
Parts of East Anglia and the South East can expect the highest temperatures next week, according to the Met Office.
Health officials have warned of the risks when taking some medicines, including ibuprofen, in hot weather.
They can make it harder for the body to stay hydrated, regulate temperature and cope with sun exposure.
Dr Alison Cave, chief safety officer at the Medicines and Healthcare products Regulatory Agency, said: "Proton pump inhibitors (PPIs), commonly used to treat acid reflux and heartburn, have also been linked to a very low risk of a lupus-like skin reaction triggered by sun exposure, and common painkillers such as ibuprofen and naproxen may also increase sun sensitivity."
In other developments, the Fire Severity Index has warned any wildfires are likely to be exceptionally severe on Sunday in almost all of the East and South East of England.
(c) Sky News 2026: UK weather: Heat record set in 1995 will likely be broken next week
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