Moderately sensitive, for small-dog reasons
The sensitivity a Bichon does have comes mainly from size and coat care. A small dog has less body mass to buffer temperature change, heats up quickly during excited play, tires sooner in heat, and walks with its whole body close to hot pavement that radiates warmth upward. Treat hot and humid as the combination that shortens this little dog's day.
The coat helps only when it is properly groomed
That cheerful white cloud of a coat is a single, continuously growing curly coat rather than a shedding double coat, and its condition decides how it performs in summer. A brushed-out, regularly trimmed coat allows air to circulate near the skin and is comfortable in warm weather. Keeping grooming appointments through summer, brushing between them, and asking the groomer for a manageable warm-weather trim, rather than a shave to the skin, keeps the coat working for the dog instead of against it.
Exercise a small dog by the clock and the pavement
Walk your Bichon in the early morning and evening in hot weather, and keep midday trips to brief, shaded toilet breaks on grass where possible. Pavement matters more to a Bichon than to a tall breed, both because paw burns are a risk on any dog and because the reflected heat bathes a short dog's belly and chest. If the pavement is too hot for the back of your hand held against it for several seconds, it is too hot for this walk.
Heat signs in a Bichon look fast and obvious once you know them
A comfortable Bichon pants lightly with a relaxed body; an overheating one pants rapidly and hard, may drool, becomes restless or, conversely, flattens out and refuses to move, and can develop a bright red tongue and gums. Vomiting, wobbliness, glazed eyes, or collapse in a small dog is an urgent veterinary situation, so cool the dog gently in shade with cool water on the body, offer small drinks, and call the vet without delay. Senior Bichons, puppies, overweight dogs, and those with heart or breathing problems should be considered high risk and kept out of hot conditions entirely. White, thinly haired areas such as ear tips and a shaved belly can also sunburn, so shade matters for skin as well as temperature.
Indoor summer life suits this breed, with planning
The Bichon is fundamentally an indoor companion, which makes summer management easier than for an outdoor-loving breed, provided the indoor space genuinely stays cool. Guarantee a cool room with airflow, fresh water in the rooms the dog uses, and a cool surface to lie on, and close curtains on sun-facing rooms that turn into heat traps by afternoon. Garden access should be supervised and shaded, with the door back inside available, because a small dog left in a sunny yard can overheat while an owner assumes the dog will simply come in. Never leave a Bichon in a parked car in warm weather, and be careful with carrying bags and enclosed carriers in the sun, which heat up quickly around a small body.
Keep every carer working to the same small-dog rules
Bichons are often cared for by a rotation of family, friends, and groomers, and summer problems tend to start with someone applying bigger-dog assumptions: a long midday walk, a sunny garden play session, a skipped grooming appointment. Share the walking hours, the pavement check, the grooming schedule, and the early warning signs in one place everyone can see. For a Bichon Frise household, KinsLe's Family Sharing gives relatives access to the dog's profile, so each person at home can look up the small companion in their own time.