The UK Health Security Agency (UKHSA) and Met Office have jointly issued the warning, which comes into effect from 10am on Wednesday, July 9 and remains in place until 10am on Tuesday, July 15.
The alert covers several regions, including London, the South East, South West, East Midlands, West Midlands, and the East of England.
While most of the country is under a yellow alert, London has been placed under an amber alert, meaning the impact on health and services is likely to be more severe.
According to UKHSA guidance, significant strain is expected on health and social care services. The risks include:
• A rise in deaths, particularly among people aged 65 and over, or those with underlying health conditions
• Increased pressure on GP surgeries, NHS 111, and emergency departments
• Overheating in care homes and hospitals, potentially exceeding safe indoor temperature thresholds
• Disruptions to community care services and staff affected by heat-related fatigue
• Higher risk to vulnerable individuals living alone or in poorly ventilated homes
Temperatures are expected to reach 28°C on Wednesday and remain at 31°C from Thursday through the following Monday, based on Met Office forecasts.
Overnight lows will stay in the high teens or low 20s, offering little relief from the heat.
Dan Holley, deputy chief meteorologist at the Met Office, said: “High pressure from the Atlantic will gradually exert its influence over the UK this week.
“We’ll see temperatures build day-on-day, with the potential for hot conditions to become quite widespread by the end of the week and into the weekend.
“On Wednesday, temperatures could reach up to 28°C in parts of England, climbing to 30°C on Thursday and 32°C by Friday.
“By this stage, heatwave criteria are likely to be met in parts of England and Wales, and in parts of Scotland over the weekend.
“High temperatures are likely to persist into the weekend, especially away from coasts with onshore winds, reaching the low 30s in portions of England and Wales, and accompanied by rising humidity and warmer nights.”
The UK has already seen record-breaking warmth this summer. July 1 saw the hottest day of the year so far, with 34.7°C recorded at St James’s Park in central London.
June was provisionally the warmest on record across England, according to the Met Office.
An official heatwave is declared when an area meets or exceeds its temperature threshold for three consecutive days. In London, that threshold is typically 28°C.
Pollen and UV levels are also forecast to be very high in the capital during this period.
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The UKHSA is urging residents to:
• Stay hydrated and avoid excess alcohol
• Keep indoor spaces cool, using blinds or curtains during the day
• Check in on older or vulnerable neighbours
• Never leave anyone, particularly children or pets, in a parked car
