A veterinarian is warning pet owners about walking their four-legged friends during extreme heat.

With lots of sun and heat this summer, many pet owners have been taking the opportunity to enjoy the outdoors with their dogs.

However, Dr. Maggie Brown-Bury is cautioning against walking pets at peak temperatures, especially on asphalt or concrete. She says it’s important to pay attention to your pet, as they can’t speak for themselves.

She says the heat from the ground can burn the pads of their feet, but they may not know how to express their discomfort other than walking faster. She says they don’t know how to say “I don’t like this.”

Dr. Brown-Bury also warns that flat-faced dogs like pugs or bulldogs are at a higher risk of heat-related illness.

As dogs do not have sweat glands, they pant to dispel heat, meaning flat-faced dogs—who have a shorter nasal passage—will feel the heat worse than a longer-snouted dog, putting them at risk of heat stress.