OLR Report 2015-R-0192 summarizes state laws prohibiting a person from leaving an animal in an unattended vehicle.
Eighteen states have laws that explicitly address leaving an animal in an unattended vehicle. These laws either prohibit a person from leaving an animal in an unattended vehicle, allow certain people (e.g., police and animal control officers) to rescue an animal that is confined in a vehicle, or both. Generally, the person may use reasonable force to rescue the animal given the circumstances. The report includes a table outlining the eighteen states and the specific prohibited activity, penalties, and rescue provisions.
In Connecticut, depending on the facts and circumstances of the case, a person leaving an animal confined in a parked vehicle in adverse weather (e.g., extreme heat or cold) may be charged with animal cruelty.
For more information, read the full report here.