UK endures hottest day of the year so far as temperatures hit 28.3C - but 31C heatwave 'is on the way' as officials issue four-day yellow heat alert

Summer has finally arrived in Britain with the hottest day of the year so far and temperatures expected to climb before they cool down, say forecasters.

The start of a likely heatwave, where the temperature reaches a certain threshold for three days, began yesterday. The Met Office said the highest reading was 28.3C (82.9F) in Wisley, Surrey, making it the UK's warmest temperature of 2024 to date.

London recorded a high of 27.4C (81.3F) at St James's Park, while the mercury rose to 27.3C (81.1F) in Aboyne, Aberdeenshire - which was also Scotland's hottest day so far.

In addition, a temperature of 25.8C (78.4F) at Castlederg in County Tyrone made it Northern Ireland's highest temperature of the year. Wales got to 24.8C (76.6F) at Hawarden yesterday, but its 2024 high remains 25.3C (77.5F) at Usk on May 12.

With the blast of warm air set to peak at 31C (88F) tomorrow in the capital, health warnings were issued - running for four days between yesterday and Thursday.

The UK Health Security Agency (UKHSA) and the Met Office issued a yellow heat alert for most of England, with all but the North East included, prompting some critics to say the warning smacked of the nanny state.

The London Fire Brigade warned the public to be on guard against wildfires breaking out due to discarded cigarettes and barbecues in the hot weather.

Pollen levels nicknamed a 'pollen bomb' has been plaguing hay fever sufferers with 'very high' levels, particularly of grass pollen in the warm, dry weather, accompanied by nettle, dock and plantain pollen too.

Oli Claydon, a Met Office forecaster, said London and surrounding counties of Essex, Kent and Surrey were among the hottest in the land.

He said: 'With 28C (82F) on Monday, 30C (86F) on Tuesday and 31C (88F) on Wednesday, London is likely to reach heatwave criteria, as are surrounding areas that have a slightly lower threshold.'

'It's not guaranteed but this will likely be towards the South-East of England, particularly London, Essex and Kent.'

The scorching weather has been labelled the 'Iberian plume' of high pressure coming up from Spain and Portugal - although it is only expected to last until Thursday, when cooler weather will arrive.

Mr Claydon added that the heat is only expected to last until tomorrow with heavy showers, thunderstorms and persistent rain possibly returning in the west as the week goes on.

To be defined as a heatwave, the temperature has to meet a threshold temperature - that varies across the country according to local conditions - ranging from 25C (77F) in Scotland to 28C (82F) in London.

The sunshine came as a welcome boost to the hospitality sector after a drizzly spring.

The licensed trade predicted sales of drinks could be boosted by as much as 20 per cent.

One veteran ice cream seller, Katy Alston known to her customers in West Sussex as Mrs Whippy, welcomed the 'wonderful' news of warmer weather.

She said: 'What we notice, once the weather's good, is everyone goes into holiday mode - so they eat ice cream, they come out, they spend longer out.

'The footfall for just a takeaway cone goes from probably 1 per cent to 100 per cent,' the former Ice Cream Alliance president added.

Emma McClarkin, chief executive of the British Beer and Pub Association, said she hoped the trade would get a boost from sunshine and the warm weather.

She added: 'The last period of sustained warm sunnier weather way back in September last year saw average increased sales of almost 20 per cent.'

Glastonbury festivalgoers can expect mostly warm, dry, settled and temperatures of 25C (77F) to 27C (81F) with cooler temperatures on Thursday and the possibility of occasional showers from Friday to Sunday.

Friday through to Sunday are forecast to be dry days, with sunny spells and light winds, although there is some uncertainty still and so the odd shower is possible.

The week's heat marks a break from the rainy spring, which saw 32 per cent more rainfall than the average in England and Wales according to the Met Office, and hampered businesses reliant on tourism or high street foot traffic.

Meanwhile the Royal National Lifeboat Institution (RNLI) issued a safety warning yesterday, reminding people heading to coastal areas to take precautions.

Sam Hughes, water safety education manager at the RNLI, said: 'We are expecting the coast to be extremely busy with this burst of warm weather.

'We want everyone to enjoy being around the water but we also want to make sure people stay safe and know what to do in an emergency.

'Always visit a lifeguarded beach and swim between the red and yellow flags. If you get into trouble in the water, Float to Live: tilt your head back with ears submerged and try to relax and control your breathing.

'Use your hands to help you stay afloat and then, once you are through the initial shock, call for help to or swim to safety if you can. In an emergency call 999 and ask for the coastguard.'