I don't know of any weather change as miserable as the monsoon, one of the main agents of aging and death in India. For dogs and cats. This is the season the kittens and puppies have to survive to live on. This is the season the older dogs have to survive without spinal nerve and brain damage, to survive lameness and paralysis, intestinal and respiratory malfunction, to survive blood poisoning and non-healing, hardening and ulceration.
The stress of weather alone is the more extreme than the moon cycle, but the monsoon is a layering of weather stress on moon cycles making the peaks more painful and the troughs deeper.