A UK study suggests that as well as man's best friend, cats, guinea pigs, rabbits and ferrets are also being taken to vets with the condition.
The researchers say their findings highlight the need for better public awareness of heatstroke and the risk to all animals, and warn that cases will continue to rise as we face warmer weather due to climate change.
The most common symptoms in all animals studied included abnormal breathing, lethargy, collapsing, and stomach issues, such as diarrhoea.
Cats seek out warm areas to sleep and can become trapped in greenhouses and sheds, the researchers say.
While caged pets such as rabbits, guinea pigs and ferrets are at risk of heatstroke due to confinement in hot accommodation, for example if their housing provides limited access to shade, or cooler temperatures, they add.
"There is a misconception that heatstroke in pets only relates to dogs in hot cars and we need to do more to raise awareness of risk factors not only for dogs but in the wider pet population," Nottingham Trent University researcher Dr Anne Carter said.
"Owners of small animals such as rabbits, ferrets and guinea pigs may need to review their pet's housing and take steps to keep their pets cool in the warmer months to reduce the risk of heatstroke."
A team at Nottingham Trent University analysed data relating to small animals seen by a group of UK vets between 2013 and 2018, as well as the triggers and risks.
They found that dogs were worst affected with 146 cases of heatstroke.
While three quarters of these cases were attributed to the dogs being exercised, and seven per cent were due to being trapped in a hot car.
Flat-faced dogs, such as bulldogs, were particularly at risk, making up a fifth of cases, the study found.
Sixteen cats were seen by vets for heatstroke, with older cats - those aged over 15 - accounting for the highest number of cases, the researchers found.
Hot weather was responsible for eight guinea pigs, three rabbits and a pet ferret being treated for the heatstroke.
The researchers found that all of the rabbits also belonged to flat-faced breeds.
Unsurprisingly, the summer months saw the highest number of vet visits for heatstroke.
Researchers say overall figures for heatstroke are likely to be far greater than reported as it can go unrecognised by owners due to a lack of awareness of the potential risks and triggers.
The study, which also involved the University of Liverpool, is published in The Open Veterinary Journal.
