Quick answer: Nighttime panting in dogs when the temperature is normal usually indicates pain or discomfort, anxiety, Cushing's disease, or in older dogs, heart or cognitive issues.
Panting is a primary response to pain in dogs. A dog that starts panting at night may have undiagnosed pain from arthritis, injury, or internal issues that becomes more noticeable when they settle down to rest. Watch for reluctance to lie in certain positions, frequent repositioning, or guarding specific body areas.
Dogs with noise phobia, separation anxiety, or generalized anxiety often pant at night when the house is quiet and sounds are amplified. If panting correlates with storms, loud events, or simply being left alone at night, anxiety is likely. Behavioral approaches and, in some cases, medication can help significantly.
Cushing's disease causes nighttime panting, restlessness, and increased thirst — more common in dogs over 6. Heart disease reduces oxygen circulation, causing panting as the body compensates. Canine cognitive dysfunction (dog dementia) causes nighttime restlessness and panting in dogs over 10.
Occasional nighttime panting may not be urgent, but persistent or worsening nighttime panting — especially in a dog over 7 — should be evaluated by a vet to rule out medical causes.