Tesco is sending staff to patrol outside its stores to check whether customers have left dogs in their cars.
The news came as temperatures soared to 32C on Monday, the hottest day of the year.
Employees have been trained to spot and treat dogs who show signs of heatstroke.
“We’re working with the RSPCA and all of our colleagues in store have received training to ensure animal welfare is protected,” a Tesco spokesperson told Birmingham Live.
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Last year, Nottingham Trent University researchers found that leaving dogs in cars could be dangerous year-round.
They found that car temperatures exceeded 25C every month, which can cause overheating in breeds with flat faces, like bulldogs and pugs.
Temperatures rose above 35C – a dangerous level for all dogs – between April and September.
“People assume the risk is only midday during the summer, when in fact cars can reach potentially dangerous temperatures all year round,” study author Anne Carter said.
The RSPCA advises people to phone 999 if a dog shows signs of heatstroke, which include drowsiness, vomiting and falling over.
Yesterday, the Met Office issued an extreme weather warning, while sources suggested the summer heatwave was set to continue into late July.
Temperatures are predicted to exceed 32C this week in London and the South East.
