The current alert follows a record-breaking June that prompted a rare red heat health alert across several UK regions.
The Met Office reported a confirmed record of 37.3C in Santon Downham, Suffolk.
Meteorologists are currently awaiting verification of a 37.7C reading in Lingwood, Norfolk.
Either measurement surpasses the previous June record of 35.6C set in Southampton in 1976.
"This has been unprecedented heat for the month of June and provides further evidence of how high temperature extremes are becoming increasingly common in the UK as a result of human-induced climate change," said Greg Wolverson, Met Office deputy chief meteorologist.
Meteorologists attributed the recent severe weather event to a heat dome that settled over western Europe before moving east.
The World Health Organization reported over 1,300 heat-related deaths across the continent during that period.
Approximately 1,000 of those fatalities occurred in France alone.
Looking ahead, forecasters predict variable cloud and sunny spells for many on Wednesday, with warm conditions in the south and east.
Thursday will see patchy rain clearing the far south, remaining largely dry elsewhere.
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Heading into the weekend, southern regions will remain dry with temperatures rising under strong sunshine, while northern regions continue facing cloud and rain.
