THE mini-heatwave is set to continue with a day of tropical temperatures ahead of a night of torrential thunderstorms expected to bring nearly a month of rain.

Swindon, Chippenham and Trowbridge are forecast to have a top temperature of 32C today, with 31C being the top temperature in Devizes and 

The mercury will rise to 29C in Scotland and 28C in Northern Ireland.

But parts of the South East could see temperatures climb as high as 35C - close to the record for July of 36.7C (98.06F).

Meanwhile there is a yellow warning of rain stretching from Tuesday evening and into Wednesday evening, with up to two inches (50mm) expected in some parts, bringing a risk of flash flooding.

Public Health England (PHE) is urging people to look out for elderly relatives and friends who may be susceptible to the high temperatures - and to take extra care of young children, babies and those with heath issues.

With the warm weather expected to last until the end of Wednesday, PHE is advising a common-sense approach to dealing with the heatwave.

People are urged to drink plenty of water and avoid dehydrating alcoholic and caffeinated drinks, close curtains to keeps rooms cool, open windows and avoid people and animals being left in closed, parked vehicles which can get extremely hot.

There are also warnings to stay out of the sun between 11am and 3pm, avoid physical exertion at the hottest times of the day and stay in the shade - and to put on a hat and wear sunscreen.

Dr Angie Bone, PHE's head of extreme events, said: "For some people - such as older people, those with underlying health conditions and those with young children - summer heat can bring real health risks.

"This summer we're urging people to keep an eye on those at risk and, if you're able, offer help to stay cool and hydrated."

St John Ambulance is urging people to be aware of headaches, dizziness and cramp which can be signs of heat exhaustion and heat stroke.

Pollen levels will be high over the country for the next few days, causing havoc for hay fever sufferers while sleeping won't be easy with temperatures expected to be 22C overnight.

The hot weather has been caused by a warm plume of air that has worked its way northwards from Spain, the Met Office said.

Wednesday will see highs reaching the low 30Cs, but by Thursday fresher conditions from the Atlantic will bring temperatures down to the more comfortable mid-20Cs, reaching around 22C (71.6F) to 24C (75.2F) by Friday and Saturday.

Met Office forecaster Sophie Yeomans said: "We are looking at probably the hottest day of the year today with quite a few places reaching 34C or even 35C in the South East.

"With all the warm and humid air it does mean we are going to have a thundery breakdown later on this evening.

"The only part to escape will be the very south of England, with lightning, hail, gusts of wind and 30mm of rain falling in the hour, but this won't be persistent.

"There's potential for nearly a month's rain in some areas during the time we have the warning."

Meanwhile, due to speed restrictions put in place by Network Rail between 1.30pm and 7pm today, GWR is warning customers to expect journeys to take longer.

Speed restrictions have been put in place throughout the main junctions in and out of London Paddington as rail track temperatures are set to exceed 50C in parts of London and the Thames Valley,

Most services are expected to operate as timetabled but some journeys may take between 10-15 minutes longer.

Customers are being advised to check before they travel, to drink plenty of water, and to help rail staff keep a lookout for the more vulnerable making journeys today.

A GWR spokesperson said: “With temperatures in London set to exceed 30 degrees, the effect can bring the temperature of the rails to over 50 degrees, and we have been asked by Network Rail to drive more slowly as a result.”  

A spokesperson for Network Rail said: “Our modern rails are far more resistant to heat expansion and buckling than they used to be. 

"However, a day this hot affects even our track, so we need to restrict speeds for safety.  Full details are available at networkrail.co.uk.”