Every summer, emergency veterinary clinics see a surge in heatstroke cases. Many of them are preventable. Almost all of them happen because someone underestimated how quickly heat can overwhelm a dog's ability to regulate body temperature.
Dogs don't sweat like humans. They cool themselves primarily through panting and through the pads of their feet. This system works adequately in mild temperatures but fails rapidly in heat, humidity, or during intense exercise. And the threshold varies dramatically by breed size, coat type, and physical build.
This guide breaks down heat safety by breed size because the risks and responses are genuinely different for a 10 pound Chihuahua versus a 100 pound Bernese Mountain Dog.
Universal Rules (All Sizes)
Before we get into size specifics, these rules apply to every dog:
- Never leave your dog in a parked car. Even with windows cracked, interior temperatures can reach lethal levels within minutes. On an 85 degree day, a car interior can reach 120 degrees in 30 minutes. This kills dogs every year. Every single year.
- Provide constant access to fresh water. Bring water on every walk, every outing, every car ride. Dehydration accelerates overheating.
- Know the signs of heatstroke: Excessive panting, drooling, bright red gums, vomiting, diarrhea, staggering, collapse. If you see these signs, move your dog to shade, apply cool (not cold) water to their body, and get to a vet immediately. Heatstroke is a medical emergency.
- Test the pavement. Place the back of your hand on the pavement for 5 seconds. If it's too hot for your hand, it's too hot for your dog's paws. On a 90 degree day, asphalt can reach 150 degrees. Walk on grass or wait for cooler hours.
- Shift walk times. Early morning (before 8am) and evening (after 7pm) are the safest windows during summer. Midday walks are risky even for healthy dogs.
Small Dogs (Under 20 Pounds)
Small dogs have a higher surface area to body mass ratio, which means they can actually overheat faster than you'd expect for their size. They're also closer to the ground, where radiant heat from pavement is most intense.
Special Risks
- Proximity to hot surfaces (their bellies and chest are inches from scorching pavement)
- Brachycephalic small breeds (Pugs, French Bulldogs, Boston Terriers) have compromised airways that make cooling through panting less efficient
- Small dogs can become dehydrated faster
Summer Strategy
- Keep walks short (10 to 15 minutes in warm weather)
- Use grass exclusively for walking surfaces
- Consider a cooling vest designed for small dogs
- Offer water every 10 minutes during outdoor time
- Watch for rapid breathing as an early warning sign
- For brachycephalic small breeds: skip outdoor activity entirely when temperatures exceed 80 degrees and humidity is high
Medium Dogs (20 to 50 Pounds)
Medium dogs have the widest range of heat tolerance because the category includes both heat tolerant breeds (some hound types, terriers) and heat sensitive breeds (bulldogs, some spaniels). Know your specific breed's tolerance.
Special Risks
- Active medium breeds (labs, spaniels, heelers) often don't self regulate and will continue playing or running past their safe heat threshold because their drive overrides their thermoregulation
- Double coated breeds retain heat in their undercoat
- Overweight medium dogs overheat faster than fit ones
Summer Strategy
- Limit intense activity to early morning hours
- Provide swimming opportunities where safe (natural cooling)
- Never shave a double coated breed (the coat actually insulates against heat; shaving removes this protection and increases sunburn risk)
- Watch drive oriented breeds carefully during play and enforce rest breaks
- Offer shade and water at all times during outdoor activity
Large Dogs (50 to 90 Pounds)
Large dogs generate more metabolic heat during activity and take longer to cool down. Their larger body mass retains heat. Many large breeds are also more prone to exercise intolerance in heat.
Special Risks
- Greater metabolic heat production during any activity
- Higher risk of exercise induced heatstroke
- Joint and mobility issues (common in large breeds) can be aggravated by heat and the reluctance to move in heat
- Deep chested large breeds have elevated bloat risk, and bloat risk may increase with excessive water consumption after exercise in heat
Summer Strategy
- Reduce walk distance by 25 to 50% during hot days
- Avoid all running, hiking, or intense play when temperatures exceed 80 degrees
- Use elevated or cooling beds indoors to allow air circulation beneath the body
- Offer multiple small water breaks rather than allowing them to gulp large amounts at once (reduces bloat risk)
- Consider indoor enrichment (puzzle feeders, training sessions) as activity substitutes on hot days
Giant Dogs (Over 90 Pounds)
Giant breeds are the most heat vulnerable dogs. Their massive bodies generate enormous metabolic heat, and their cooling systems are proportionally inadequate. Breeds like Great Danes, Mastiffs, Saint Bernards, and Newfoundlands are particularly at risk.
Special Risks
- Extremely high metabolic heat production
- Slow cooling time after any exertion
- Cardiac stress from heat exposure (giant breeds are already prone to heart conditions)
- Increased bloat risk in heat and during panting
Summer Strategy
- Exercise only in the coolest part of the day (early morning preferred)
- Keep walks gentle and short during any warm day
- Air conditioning is not optional; giant breeds need a reliably cool indoor environment
- Provide multiple water stations throughout the house
- Use kiddie pools or sprinklers for supervised outdoor cooling
- Monitor breathing rate and gum color frequently during summer months
Senior Dogs of Any Size
Older dogs have diminished thermoregulation regardless of size. Their cardiovascular system is less efficient, their respiratory function may be compromised, and chronic conditions (arthritis, heart disease, kidney disease) all reduce heat tolerance.
- Treat any dog over 8 as heat sensitive regardless of their previous tolerance
- Maintain hydration aggressively (add water or broth to food if they're not drinking enough)
- Ensure supplements and medications are given consistently (joint support is especially important because heat can increase inflammation perception)
- Provide cool, comfortable indoor spaces with orthopedic bedding
- Watch for signs of heat distress at lower temperatures than you'd expect
Emergency Response
If you suspect heatstroke:
- Move to shade or air conditioning immediately
- Apply cool (not ice cold) water to the body, focusing on the neck, armpits, and groin
- Place cool wet towels on these areas (but replace them frequently; they warm up fast)
- Offer small amounts of cool water to drink (don't force it)
- Get to a veterinary emergency clinic as fast as safely possible
- Do NOT use ice or ice water (can cause blood vessels to constrict, trapping heat inside)
Heatstroke can cause organ damage even after the dog appears to recover. Always have a vet evaluate your dog after a heat event.
Summer should be fun for your dog. With the right precautions adjusted for their size and build, it can be. Know your dog's limits, respect the heat, and when in doubt, stay inside and play puzzle games instead. Your dog would rather miss a walk than end up at the emergency vet. Trust us on that one.