A black coat over a heavyweight engine
A Rottweiler in a heatwave is fighting physics on two fronts. His coat is predominantly black, and black absorbs solar radiation rather than reflecting it, so a Rottweiler standing in full sun is heating from the outside in. Underneath, he carries one of the heaviest, most muscular frames of any common breed, and muscle generates heat in proportion to its mass while he works. A big dog also has less surface area relative to his volume than a small one, so the heat he makes during a walk leaves slowly. Add the breed's dense undercoat beneath the glossy top layer, and a hot Rottweiler stays hot long after he reaches shade.
Exercise like the weather is in charge
Rottweiler exercise in a heatwave belongs to the first and last hours of daylight, on routes chosen for shade and grass rather than distance. Cut the distance as well as the hour: a dawn walk at two-thirds his usual length, at a steady plod with sniffing stops, tires a Rottweiler more safely than a short sharp burst of play. Cancel fetch and tug games outdoors at midday entirely, because this breed's play drive and desire to please will keep him working while his temperature climbs. Mental work indoors — training refreshers, food puzzles, a frozen chew on a cool floor — fills the gap his muscles would rather fill dangerously.
Water in volume, and a place to be wet
A Rottweiler drinks in volume in hot weather, so his bowl needs checking far more often than a small dog's: a bowl emptied by ten in the morning and left dry until evening is a genuine heatwave hazard in a dog this size. Many Rottweilers enjoy water — a garden hose game at dawn, a sturdy paddling pool deep enough to lie in, or a walk built around a safe swimming spot all cool him through the belly and chest. Wet his chest, belly, and the skin inside his thighs when he comes in hot rather than soaking his back, and let a fan play on him as he dries on a hard floor.
Strength changes the escape calculation
A bored, overheated Rottweiler restless in a hot house or a shadeless garden is a dog with the strength to act on his frustration. Rottweilers can lean through a rotten fence panel, shoulder open a gate with a tired latch, or dig out under a fence toward a cooler, more interesting world. Before the hottest days, walk the boundary and fix what you find, keep him indoors in the cool during the midday peak rather than exiled to the yard, and make sure his collar and ID are on: a dog of his size and reputation needs to be identifiable and contactable fast if he does get loose, for his safety as much as anyone's.
The signs, and getting word out if he slips away
In a Rottweiler, overheating shows as panting that becomes harsh and effortful, ropes of thick drool, gums turning dark red or feeling dry, restlessness that flips into dullness, and any unsteadiness on his feet. Cool him with cool water and airflow, and phone a vet immediately rather than monitoring at home: a dog of his mass stores heat so well that he can keep worsening after the walk ends. If restlessness ever does beat your fencing during the hot spell, KinsLe's Lost Pet Alert System sends a free alert to nearby Circle of Love members straight away, and anyone who spots your Rottweiler can message you directly through his profile to get him home.