The working pit bull, can withstand the heat quite well and run all day in the heat if given proper shaded area and fresh water in a large enough bowl to re-hydrate from time to time.

The working dogo argentino can run all day as well in the heat if given the proper shaded area as well and fresh water with a large enough bowl to re-hydrate from time to time. The dogo you may have to monitor a little bit more than the pit bull because the dogo has a white coat and is more susceptible to skin cancer.

The lighter weighing working Tosas ranging from 80 to 90 lbs imported from Japan lines will also run all day and same as above with water and shade.

Basically you want a dog that is from working lines and with a long enough muzzle as mentioned before and add in the trait of excellent cardio and coat color that reflects the sun instead of attracting the sun. A black coated dog may have a tougher time cooling down than a brown, red or brindle color dog.

Purchase an inexpensive kiddie plastic pool from Walmart and fill it with water and put it in a shaded area. This will give your dog of choice an additional area to cool down it's temperature.

Sometime you will see your dog digging in the dirt let him. The innate ability for a dog to dig gives him the ability to lay in the dirt which is cooler than the dirt on the surface. This will also cool your dog down. After the dog is done cooling and moves on from the dirt recover it later on in the day.