28 states have laws that either prohibit leaving an animal in a confined vehicle under dangerous conditions or provide civil immunity (protection from being sued) for a person who rescues a distressed animal from a vehicle.
Most laws provide that the animal must be confined or unattended in a parked or stationary vehicle. For a person to violate the law, the conditions in the motor vehicle have to endanger the animal's life. Some of the statutes specifically state that extreme hot or cold temperatures, lack of adequate ventilation, or failing to provide proper food or drink meet this definition. Other laws simply state that the conditions pose an imminent threat to the animal's health or safety.
States with such laws typically allow rescue of the animal from the vehicle. This may involve forcibly entering the motor vehicle to remove the trapped animal. The majority of states limit their "rescue" laws to law enforcement, firefighters, animal control, first responders, or authorized humane officers. Recently, about 12 states have enacted laws that allow any person to rescue a distressed animal (AZ, CA, CO, FL, IN, KS, MA, OH, OR, TN, VT, and WI). These laws function to limit the civil or criminal liability of the person for damages resulting from the forcible entry of the vehicle. Indiana is the first and only state to require the person who forcibly enters a vehicle to rescue an animal to pay half the damages. West Virginia and New Jersey are the only states that criminalize the act of leaving a pet unattended under dangerous conditions without providing a rescue and immunity provision for anyone.
With these new rescue laws, most require would-be rescuers to follow a number of steps. For instance, these laws may require that people first ensure the vehicle is locked and forcible entry is the only means to retrieve the animal. The person may be required to first call 911 or local enforcement before entering the vehicle. The law may require that a note is left indicating the safe location of the animal and that the person remains on scene until law enforcement or other first responders arrive.
Penalties for leaving an animal unattended in a motor vehicle under dangerous conditions vary from state to state. A few states make it an immediate fine like other civil infractions. The rest of the states assign a misdemeanor penalty, with fines ranging from a couple hundred dollars to thousands of dollars. Some list possible jail time or imprisonment. New Hampshire makes a second conviction a felony offense.
While not all states have laws that address animals in parked vehicles, numerous local ordinances prohibit this, and more may be enacted. Even without a state or local law, this action could still constitute cruelty under some circumstances. In fact, in the Texas case of Lopez v. State, the defendant left his dog in his car on a hot day to go and watch a movie in a theater. He was ultimately convicted under the state's anti-cruelty law. Notably, Texas does not have a statute that specifically addresses dogs left in parked vehicles.
A few years back while traveling I ran across a distressed pet. It was incredibly hot out and I ended up breaking into the car before the police arrived. I ended up having to pay 50% of the broken window, a small price for saving the pet. Laws are getting better and better to protect the pets, but everyone keeping an eye for stranded animals will be far more effective.
So remember, 70 degrees is too hot and it can take only a few minutes to cause serious harm to an animal. Keep your pets safe and watch out for others in harms way!