Humane League of Lancaster County issued a cold-weather advisory Friday for pet owners who typically keep animals outside.

Pet owners should bring animals inside to heated, protected areas because dog houses adequate in normal temperatures don't protect animals from frostbite and hypothermia.

Unheated garages do not provide additional protection, as the pet cannot generate enough body heat to keep the space warm. Instead, provide a smaller shelter within the garage to keep pets alive.

The American Animal Hospital Association reports animals are vulnerable to frostbite and hypothermia in less than an hour. Young or older animals and those with health conditions such as diabetes or kidney disease are especially vulnerable to winter weather. Regardless of their health, no pets should stay outside for unlimited amounts of time in freezing cold weather.

The AAHA also suggests that pet owners who must take animals outside shouldn't leave them unattended. A rule of thumb, when you're cold enough to go inside, they probably are too.

If pets absolutely must be left outside for a significant length of time, make sure they have a warm, solid shelter elevated above the ground that protects them from the wind, thick bedding and plenty of nonfrozen water served in plastic containers, not metal. Try leaving out a hot-water bottle, wrapped in a towel so it won't burn your pet's skin.

Keep in mind it is illegal to keep pets outside without adequate shelter and food. In Friday's bitter temperatures, police were responding to reported cases of animals left outside for long periods of time.