A heat-health alert has been issued as a heatwave that could see temperatures soaring to 32C is set to hit the country.

The UK Health Security Agency (UKHSA) and the Met Office have increased the Level 2 alert to Level 3 for the south east, London and east of England as forecasters predict highs of 32C (89F).

Level 3 means you should look out for others, especially older people, young children and babies and those with underlying health conditions and curtains should be closed on rooms that face the sun.

Advice on how to reduce the risk can be obtained from the Heatwave Plan for England page, from your doctor or local chemist, or ring NHS 111.

A Level 2 alert is also now in place for the south west, east Midlands, west Midlands, north west and Yorkshire and the Humber regions.

The alerts will be in place from 9am on Monday until 9am on Friday, during which time the UKHSA recommends drinking plenty of fluids and avoiding excess alcohol, avoiding physical exertion during the hottest part of the day, and taking special care to check in on the vulnerable and the elderly who find the heat particularly challenging.

The announcement came after the temperature reached 28.5C (83F) in St James’ Park, London, today, which made the capital hotter than Los Angeles and Santorini.

Dr Agostinho Sousa, head of extreme events and health protection at the UKHSA, said: “Heat-health alerts have now been issued to the majority of the country, with temperatures set to remain consistently high throughout the duration of next week.

“Most of us can enjoy the hot weather when it arrives, but it is important to keep yourself hydrated and to find shade where possible when UV rays are strongest, between 11am and 3pm.

“If you have vulnerable family, friends and neighbours, make sure they are aware of how they can keep themselves protected from the warm weather.”

The Met Office expects many counties in the south west, including Devon, Dorset and parts of Wiltshire, to have marked the first day of a heatwave, with much of the rest of the country to follow suit from Sunday.

The Met Office’s definition of a heatwave is when a location records a period of at least three consecutive days with daily maximum temperatures reaching or exceeding the heatwave temperature threshold, which varies by county.

In such conditions, the Met Office issues a heat-health warning which gets sent on to health and social care professionals, so they can work to minimise the impact of the high temperatures on people’s health.

Meteorologist Annie Shuttleworth said: “We’re at the start of a potentially relatively long spell of warm weather for much of the UK away from the far North West where it’s likely to be a bit cooler and cloudier.”

She added: “For some areas, namely parts of the South West, this is probably the start of their heatwave, but for the more widespread heatwave threshold temperatures to be met it’s likely to be from Sunday, so Sunday, Monday, Tuesday.”

The hottest day of the year so far was during the last heatwave on June 17, less than three weeks ago, when a temperature of 32.7C (90F) was reached.

Ms Shuttleworth added that temperatures will “come close” to this year’s high in London and the South East at the start of next week.

Parts of Scotland and Northern Ireland will also be seeing balmy temperatures, as across Aberdeenshire and Fife temperatures could be close to 27C or 28C, with 25C (77F) expected across Northern Ireland.

The hot summer days are to also usher in hot and “sticky” nights, and Ms Shuttleworth urged Britons to “keep the curtains closed during the day, especially if you’ve got a south-facing bedroom” and “keep ventilation going around your house through the day”.

The warm weather looks to be settling in for some time to come, according to Met Office forecasting, with a chance that the UK could see one of the longest heatwaves ever.

Ms Shuttleworth said: “If we see over nine days of temperatures staying above 28 degrees then it would be the longest since 2018.”

She warned there was a lot of uncertainty around what temperatures will be seen after Thursday, but it is nonetheless likely that it will remain warmer than average for the month.

The average temperature for July is around 20C.