Yellow heat health alerts have been issued for most of England with temperatures set to climb as high as 33C by the weekend.

Yorkshire and The Humber, East Midlands, West Midlands, East England, the South East, the South West and London are all covered by the alert which comes into force at 12:00 BST on Wednesday and lasts until 18:00 BST on Sunday.

Temperatures are set to be as high as 28C in London on Tuesday, with an area of high pressure building across the UK likely to bring the first heatwave of 2025 later in the week.

A yellow alert is the lowest behind amber and red on the UK Health Security Agency’s (UKHSA) system, but warns of possible impacts on health and social services.

Temperatures across the UK will continue to climb with the weather becoming increasingly hot and sunny, meaning it is likely heatwave conditions are met in some parts at the end of the week and into the weekend – although there is a chance it could extend into next week.

Many parts of the UK will see temperatures range between 25C and 30C, with some areas potentially reaching up to 33C, for example in London.

While such heat is not unprecedented this early in the summer, it is still considered quite intense.

The UK’s June temperature record stands at 35.6C, set in Southampton in 1976, and current forecasts suggest that this record is unlikely to be broken this time.

The UKHSA said an increase in demand for health services by vulnerable people is likely, as well as an increase in risk to health for individuals aged over 65 years or those with pre-existing health conditions, including respiratory and cardiovascular diseases.

Internal temperatures in hospitals, care homes and independent accommodation could also pose a risk to vulnerable people.

The heat alerts are issued to give early warning to the health and social care sector, carers and government departments when high temperatures are likely to impact on people’s health and wellbeing.

Dr Agostinho Sousa, head of extreme events and health protection at UKHSA, said: “Our findings shows that even moderate heat can result in serious health outcomes, especially for older adults, and it is therefore important that everyone takes sensible precautions while enjoying the sun.”

Making a plea to people with vulnerable family, friends and neighbours, he said: “It is important to check in on them and ensure they are aware of the forecasts and are following the necessary advice.”

All of the affected areas excluding Yorkshire and the Humber have been given a risk score of 10 out of a possible 16, meaning “significant impacts are possible” due to high temperatures.

The UKHSA’s website says this includes a possible rise in deaths, particularly among those aged 65 and over or with health conditions.

Yorkshire and the Humber’s score of seven means that only minor impacts are likely.

Little rain is forecast throughout the period, however the high temperatures may trigger a few isolated but intense thunderstorms on Saturday and Sunday, potentially occurring almost anywhere in the UK.

The heatwave is expected to break down into next week, although southern areas of the UK may remain very warm.

There are also signs that, after a brief period of relief, the heat may return soon after.

The body representing the hospitality industry said the hotter weather is a “welcome lift” for the sector.

Kate Nicholls, chief executive of UKHospitality, said: “Businesses will now be hoping for a strong summer to help counterbalance the significant cost pressures they’re contending with.”

Katy Alston, who runs an ice cream parlour near the beach in Bognor Regis, West Sussex, said: “We get so excited because this is what we wait for.

“People who work in ice cream vans are risk takers because you never know when that big yellow ball is going to come out.”

Meanwhile, the London Fire Brigade pointed to recent examples in California and South Korea in its warning over wildfires, following one of the driest springs on record in the UK and ahead of the possible heatwave.

Charlie Pugsley, deputy commissioner for operational policy, prevention and protection, said long periods of hot and dry weather “can greatly increase the risk of a grass fire” and could spread rapidly.