Officials believe there is a 90 per cent chance of a heatwave occurring in some regions, especially in eastern England where temperatures will be highest.
The heat health watch service is designed to help healthcare professionals manage periods of extreme temperature.
The service acts as an early warning system forewarning of periods of high temperatures, which may affect the health of the UK public.
Officials believe level three criteria will be met over the weekend, as temperatures rocket.
The amber alert will prompt social and healthcare services to reach out to high risk groups, such as the elderly.
“High pressure will build across England, bringing very warm or hot conditions to many parts of the country during Saturday and Sunday,” a Met Office spokesperson said.
“Highest temperatures look to be across eastern England, with western parts turning less hot Sunday.
“Into Monday, fresher air is now expected to gradually move eastwards across the country, although it will remain very warm for some eastern parts.
“If there’s anybody you know, for example an older person living on their own, who might be at special risk, make sure they know what to do.”
Temperatures will gradually build until Sunday, when they are expected to reach the high 20s across much of the UK – and even 30C in some isolated spots.
The warmest bank holiday Monday on record is 28.2C, set at Holbeach in Lincolnshire in 2017.
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Additional reporting by agencies