Warnings and health alerts have been issued as temperatures continue to soar, as the heatwave caused train tracks to warp and wildfires to spread in parts of the UK.

Monday was the hottest day of the year so far, with thermometers reaching 30.1C, but forecasters expect that record to be beaten and have issued a weather alert to warn people to stay safe as temperatures continue to rocket.

Commuters could also expect delays and disruptions as trains are put on a “go slow” due to buckled train tracks and signalling failures.

Emergency services are also warning people that swimming in open water can be dangerous after a man died in a lake in Surrey, a woman drowned while swimming in the sea in Sussex and a child went missing in a lake in Stoke-on-Trent.

The body of a man was recovered from a lake near Redhill in Surrey after he was seen struggling in the water, while in Stoke-on-Trent a major search operation has resumed this morning after a 13-year-old boy went missing in a lake.

In Eastbourne, a woman drowned while swimming in the sea. After being pulled from the water, paramedics unsuccessfully tried to resuscitate her before she was declared dead at the scene.

Surrey Police said: “Bodies of water may look safe, but can hide dangers such as hidden currents, hazardous objects, pollution and cold water shock, which affects our ability to swim and reach safety if experiencing difficulties.” 

The Met office, in conjunction with Public Health England, issued a heat health watch alert for parts of England.

“Hot weather can cause problems for vulnerable people such as older people or those with underlying health problems. More people are admitted into hospital when the weather is so hot so the alert is to make sure people are aware and can take measures to protect themselves or family members,” Alex Burkill, a meteorologist for the Met Office, said.

The weather is going to continue to be hot throughout the week, Burkill said, with Merseyside being the area that could Monday’s record and it could reach 31C or even 32C there. 

Burkill said: “With a lot of hot and sunny weather today, it’s probably going to be even hotter than yesterday, especially in the west. Tomorrow could see similar temperatures around much of England and Wales and again it’s likely to be higher in the west.

“The temperature will also rise tomorrow across parts of Northern Ireland and southern Scotland, which could also reach the low 30s.

“It’s worth pointing out that Northern Ireland’s all time record is only 30.8C and there is a chance that could be exceeded on Wednesday or Thursday. It’s an an unusual spell of hot weather for them.”

The rest of the week will remain hot and sunny, but temperatures will begin to dip over the weekend with some thundery showers predicted.  

Dr Owen Landeg, of Public Health England, said: “Much of the advice on beating the heat is common sense and many people will want to enjoy the long spell of warm weather in the forecast.

“Now is a really good time to think about what you can do to protect you and your family and friends’ health during summer. For some people, such as older people, those with underlying health conditions and those with young children, the summer heat can bring real health risks.”

Landeg urged people to keep an eye on friends, family or neighbours who may need support. 

He added: “If you’re going outside for a prolonged period, remember UV is high at this time of year so think how the sun affects you and what you’d do to make sure you don’t get burned.”

On Monday evening, thousands of commuters faced travel chaos on Monday evening, as soaring temperatures crippled Britain’s railway network.

Signalling failures caused by the hot weather were blamed for disruption between London’s Euston and King’s Cross stations and the major commuter belt around Hertfordshire.

Speed restrictions were introduced on some lines after 11am each day until Friday as Network Rail’s activated its extreme weather action teams across the country to monitor ‘vulnerable locations’.

Andy Thomas, managing director of England and Wales at Network Rail said: “On very sunny days, rails in direct sunshine can be as much as 20 degrees centigrade above air temperature causing the steel to expand markedly and could, if not carefully monitored and action taken, buckle causing travel disruption.

“Our engineers and specialist extreme weather teams are monitoring track-side temperatures and vulnerable locations and will, if necessary, introduce temporary speed restrictions during the hottest part of the day to keep trains running, albeit more slowly than normal.”

In the Peak District, hot weather and light winds helped a fire to spread on Saddleworth Moor on Sunday, where temperatures reached 25C.

Firefighters were able to get the blaze under control before it started again on Monday morning, Manchester Evening News reports.