As the country experiences temperatures of around 30C, dogs left inside cars could suffer potentially fatal heatstroke.
Tesco staff will now patrol carparks outside their stores to check for dogs in trouble.
The supermarket chain – in collaboration with the RSPCA – has trained its staff to know what to look out for if they spot a dog in difficulties.
This includes what action to take if a dog shows signs of a heatstroke, which the charity says could be heavy panting, drooling, lethargy and vomiting.
Last year, dog welfare experts at Nottingham Trent University found that leaving dogs in the car can even be dangerous all year round. Scientists monitored internal temperatures of cars in the UK, without dogs inside, every day for two years.
They found temperatures exceeded 25C in every month of the year, which is enough to cause overheating in breeds with short snouts. During further research, they also found internal car temperatures exceeded 35C between April and September, which is hot enough to cause overheating in all dog breeds.
Temperatures rose to this level on almost a third of all days from May to July, while internal temperatures in vehicles peaked between 4pm to 5pm.
The researchers said most dogs are comfortable at temperatures of between 59F (15C) and 77F (25C). However, this this is dependent on breed, coat length, fitness and other factors.
Dr Anne Carter, a senior lecturer at Nottingham Trent University, said: “Our work shows an even bigger risk to leaving dogs in parked vehicles than previously thought.
“People assume the risk is only midday during the summer, when in fact cars can reach potentially dangerous temperatures all year round, with late afternoon the hottest time period.”
“As heatstroke can be fatal in dogs, public awareness campaigns should consider launching in April or earlier.”
Extreme temperatures in the UK have also been hot enough to cause some older roads to melt. In Gloucestershire, the County Council has been carrying out emergency works in Tewkesbury as parts of the A38 began to do just that.
The situation is similar in other parts of the country, including several roads in Somerset, which have also required emergency work due to melting.
Paul Boss, chief executive of the Road Surface Treatment Association (RSTA), said: “Many roads made from asphalt do not melt in extreme heat because they are protected by a material called bitumen, which does not melt until it reaches a very high temperature.
“Some older roads can suffer from vehicle wheel track damage as a result of heavy goods vehicles, but now modern asphalts are produced and laid in such a way that this does not happen on roads resurfaced over the last 25 years to 30 years, so drivers do not need to be concerned
“Further treatments applied to the road surface regularly throughout its life help stop cracks and water getting into the road, preventing potholes forming.”
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