London has already recorded the hottest day of the year so far after an amber heat health alert was issued for the whole of England.
The temperature of 30.1C was recorded in St James’s Park at lunchtime on Thursday.
Several hours earlier the UK Health Security Agency's (UKHSA) issued its amber warning saying “significant impacts” are expected from the soaring temperatures in the coming days “including a rise in deaths”.
The alert, the first of its kind issued since September 2023, is in place until 9am on Monday.
An amber alert indicates that weather impacts are likely to be felt across the whole health service, with potential for the whole population to be at risk.
The latest warning states: “Significant impacts are likely across health and social care services due to the high temperatures, including a rise in deaths, particularly among those ages 65 and over or with health conditions.There may also be impacts on younger age groups.”
A previous UKHSA yellow warning, the lowest heat-health level, came into force at midday on Wednesday but has been upgraded as temperatures continue to climb.
London is expected to see among the hottest temperatures on Thursday with the mercury hitting 32C.
It marks the start of a heatwave with thermometers set to hit 33C (91F) in the capital on Saturday, the Met Office predicts.
Temperatures as high as 34C have been forecast for eastern parts of England.
The UK Health Security Agency has issued health warnings particularly for the vulnerable and elderly across England.
Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: "Our findings show that heat can result in serious health outcomes across the population, especially for older adults or those with pre-existing health conditions.
"It is therefore important to check on friends, family and neighbours who are more vulnerable and to take sensible precautions while enjoying the sun.
"The forecasted high temperatures may also lead to an increasing demand for remote health care services and an impact on the ability of services delivered due to heat effects on the work force."
After a scorching night, temperatures rose quickly on Thursday morning, hitting a balmy 26C (79F) by 11am.
By late afternoon, the Mercury will have risen even further, peaking at 32C (90F) at around 5pm, the forecaster added.
Bedtime will also be uncomfortable for many, with temperatures possibly staying above 22C (72F), known as a “tropical night”.
In London, a heatwave is triggered when a location records at least three consecutive days where the daily maximum temperature meets or exceeds 28C (82F).
The current warmest day of 2025 was last Friday when Santon Downham, Suffolk recorded a high of 29.4C (84.9F).
A temperature of 29.3C (84.7F) was recorded at St James' Park on Wednesday evening, almost matching the record for 2025.
The Met Office’s Dan Holley said the heat is the ”dominant story” for the next few days before possible thunderstorms arrive next week.
Londoners will hope to keep the barbecues firing all summer long after forecasters predicted a month of warm weather.
Next week looks set to bring more dry, sunny weather, with highs ranging between 24C (75F) and 27C (81F).
The high temperatures are down to a developing area of high pressure from the Azores, making London hotter than European holiday hotspots such as Ibiza and the Algarve.
Meanwhile, a report by meteorologists said there was a 50:50 risk of UK temperatures exceeding 45C (104F) in the next 12 years.
The UK's June temperature record stands at 35.6C (96.1F), set in Southampton, Hampshire during the infamous 1976 heatwave.
