Following the balmy forecasts, Public Health England (PHE) are urging caution over the coming days and nights.
Dr Thomas Waite, from the extreme events team at PHE, said: “Because the heat is going to arrive very soon, think today about what you can do, and for those around you, to stay cool during the daytime and particularly at night.
“Much of the advice on beating the heat is common sense and for most people there’s nothing to really worry about. “But for some people, such as older people, those with underlying health conditions and those with young children, summer heat can bring real health risks.
“To keep homes and sleeping areas cool at night remember to close curtains on windows that face the sun during the day, once the sun is off windows open them up to get a breeze and think about turning off electrical devices all over the home as they can generate unwanted heat too.”
But what does the Level 2 heat-health alert mean exactly? Well, it’s because there’s a high chance that temperatures will hit certain temperature thresholds for at least two days and the intervening night.
And the high temperatures predicted means that Britain could be as warm as Bangkok in Thailand, and hotter than forecasts for Madrid and Los Angeles.
The last time temperatures soared above 30C (86F) in September was in 2006 in Kew Gardens – it hit 30.5C (87F) on September 11.
If the mercury rises above 31.6C (88.9F), which was reached at Gatwick on September 2 1961, then it will be the hottest day for 55 years.
The highest September temperature recorded was in 1906 when the mercury hit 35.6C (96.1F) in Bawtry, South Yorkshire.
It won’t be as hot as London everywhere, but most of England will bask in temperatures in the high 20s. Scotland will also enjoy the warmth with Aberdeen and Glasgow possibly seeing 20C (68F) to 23C (73.4F), and there is a chance Aviemore could hit 24C (75.2F).
Dr Waite added: “The hot weather won’t make life difficult for all of us; indeed, many of us will make the most of it when the sun shines. But some people may not be able to adapt to the extra strain hot weather will put on their bodies and may feel the ill-effects.
“Each year we hear stories of people who have fallen seriously ill because, even though it’s hotter, they may wear clothes which are too warm for hot weather, they may not drink enough or just try to do too much.”