dog left in a car had to be rescued by police on Monday (July 18) on one of the hottest days of the year in the UK.Six officers smashed in through the rear window of an Audi after the pooch had been spotted in the vehicle with its owner leaving no windows open despite the sweltering heat.As the mercury reached the high 20s during late morning, the half-dozen Hertfordshire Police officers saw a crowd form at the town centre car park as they eventually broke in and freed the animal from the boiling car.READ MORE: Missing boy, 14, thought to have drowned in River Thames - as 5 others die in heatwaveLocal resident David Stuckey told MailOnline: “I was just walking back to my car and could see a large crowd of people who were stood there in disbelief.“Someone went shopping and left their dog inside the car in sweltering heat with no windows open. Everyone couldn’t believe it.“It happened at about 11.30am and it was already very warm but I don’t know how long the dog had been in the car.”He added that he was unsure what sort of breed the dog was or what condition it was in when the officers removed it from the car.The RSPCA say that the temperature inside a car can increase to double that outside the vehicle in just an hour if there is no ventilation.They also say that dogs should never be left alone in a car during hot weather, while they can also die from heatstroke if left.“When it's 22C outside, the car could reach an unbearable 47C within an hour.