The RSPCA is warning owners not to even take their dogs on short walks during high temperatures. The charity said that while many people know not to leave their pets in the car or take them for long walks in the heat, they could still be putting them at risk by going out for short walks.
The warning comes as the UK recorded the hottest day of the year so far on Wednesday.
And the weather is forecast to get even hotter with the mercury expected to reach a sizzling 34C on Friday.
RSPCA dog welfare specialist Esme Wheeler told My London: “The truth is walking dogs in hot weather can be a silent killer.
“While the majority would never leave our dogs in a car on a hot day, or even take our dogs for a really long walk in the heat, many people may still be putting their dogs at risk even on a short walk, or taking them to places such as fields and beaches with little or no shade.
“We have long-campaigned that dogs die in hot cars, but this year we’re highlighting that dogs die on hot walks, too.
“The message remains very simple – never leave a dog in a hot car because ‘not long’ is too long, and when it comes to walks, ‘if in doubt, don’t go out.'”
Dr Dan O’Neill, associate professor companion animal epidemiology at the Royal Veterinary College, echoed the RSPCA’s warning about dog walks in the heat.
He said: “Heat-related illness can lead to organ failure, brain damage and ultimately death.
“Most people know that dogs die in hot cars, but the reality is that more than 10 times as many dogs need veterinary treatment for heat-related illness following exercise as for being overheated in cars.
“It can take weeks for a dog to acclimatise to hot weather, so after a spell of cold weather, periods of hot weather can be particularly dangerous.”
Every summer the RSPCA receives hundreds of reports of dogs left in sweltering cars, over exercised in the heat and with burns on their paws from pavements.
The charity advises walking early morning or late evening when temperatures are cooler, or even skipping a walk.
Older dogs, those with thick fur, flat-faced breeds and those who already have health conditions can be more at risk.
Owners should check the pavement is not too hot by testing if they can comfortably hold their hand on the ground for five seconds.
Other tips from the RSPCA to keep dogs cool include having a paddling pool, using a damp towel for them to lie on and adding ice cubes to their water.
The charity is also urging people to be aware of the signs of heat-related illness so they can seek veterinary care if necessary including excessive panting, unusual breathing noises, lethargy, stumbling, and a blue or grey tinge to the gums or tongue.
The warning comes as a scorching 28.2C was recorded at Kew Gardens, south-west London, on Wednesday.
Forecasters are expecting an even higher 29C in the capital on Thursday.
The hot spell in parts of Britain is set to build to a “crescendo” on Friday with the mercury expected to hit 34C in south-east England.
Temperatures between 27-30C are forecast across most of England and Wales.