Dogs and cats have become major parts of millions of American families, and when summer brings hot weather and vacation travel, pets need some special attention.

Summer means added hazards for pets, from heatstroke to the problem of heartworms. But, with help, pets can cope. They can even go along on most vacation trips, according to pet care experts.Probably the biggest hazard faced by pets in the summer is overheating, particularly if left in an automobile, even for a brief period.

"On a warm day, the temperature in a parked car can reach 160 degrees in a matter of minutes, even with partially opened windows," warns the Humane Society of the United States. "With only hot air to breathe, your pet can quickly suffer brain damage or die from heatstroke."

The simple answer is don't leave the pet alone in a parked car. Leave them home when on a trip to the store or other errand.

If dogs are left outdoors, make sure they have shade available and fresh water - check the yard at all times of the day, to be sure shade is always available.

Cats, says the Humane Society, should be kept indoors all year - it keeps them from overheating, from getting run over by cars and from other hazards.

Joggers and beach fans also need to remember that what's fun for them may be dangerous for a dog.

Canines will try and keep up with a jogging master, and an out-of-shape pooch can injure itself by pushing beyond its limits. And dogs were simply not built for the beach, where there is little shade and they can overheat, burn the pads of their feet and be attacked by sand fleas.

As humidity goes up, dog heat tolerance goes down, and dogs don't sweat to relieve the heat the way humans do, according to animal care specialists at the Department of Agriculture.

As to summer's more routine problems, here are some thoughts from the federal Food and Drug Administration:

-Heartworms are a major danger in summer and can cause death to a dog. They are transmitted by mosquitoes and are most common in warm areas, but are spreading. Have dogs checked by a vet and then begin use of preventive medication.

-Fleas and ticks can cause major discomfort and may carry disease. Special soaps, collars, powders and sprays can help, but be sure to get the brand labeled for your pet - don't use dog sprays on a cat, for example. Serious cases may require veterinary care.