Hot Weather:small dogs, vs big Dogs.

Big Dogs vs Small Dogs:
it calls: "Surface to volume ratio". Big dogs have higher body mass than little dogs.This gives them a greater difficulty to cope with hot or cold weather.
Puppies for instance do not have the body mass to survive rapid dehydration. Next in line are small dogs, and up.

So, leave your Papillon  in the cool house with you, forget about the daily noon, or late afternoon, walk.
It will get cool soon enough.