Health warnings have been made ahead of what could be the hottest September day in the UK for more than 50 years.
Temperatures in the upper 20Cs have been forecast in England until Friday, with London possibly reaching 31C (88F) on Tuesday, the Met Office said.
The East of England, the South East, and the East Midlands are also expected to have some of the hottest weather.
Public Health England and NHS England have both urged caution, saying the weather can pose a risk to health.
NHS England has declared a level-two heat alert, which means there is a high chance that an average temperature of 30C (86F) by day and 15C (59F) overnight will occur over the next two to three days.
These temperatures can have a “significant effect” on a person’s health if they last for at least two days and the night in between, it said.
The last time temperatures were above 30C (86F) in September was in 2006 in Kew Gardens, which hit 30.5C (87F) on 11 September.
If temperatures rise above 31.6C (88.9F), which was reached at Gatwick on 2 September 1961, then it will be the hottest day for 55 years.
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.”
Aberdeen and Glasgow will possibly see temperatures of 20C (68F) to 23C (73.4F), and there is a chance Aviemore could hit 24C (75.2F).
The high temperatures predicted means that Britain could be as warm as Bangkok in Thailand, and hotter than forecasts for Madrid and Los Angeles.
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.”
Dr Waite advised people to close curtains on windows that face the sun during the day, and to open windows once the sun is no longer on them to get a breeze.
He added that people should think about turning off electrical devices, as they can generate unwanted heat.
Read more: http://www.bbc.co.uk/news/uk-37345436