Never leave your dog in the car on a hot (or even warm) day. 
“When temperatures outside range from 80 degrees to 100 degrees, the temperature inside a car parked in direct sunlight can quickly climb to between 130 to 172.”
– Centers for Disease Control and Prevention
http://heatkills.org/how-hot/
We all love spending time with our pets, and many dogs love to go on car rides. But as we head into summer and temperatures begin to rise, we need to carefully consider the potential ramifications of bringing our furry friends along. Especially if waiting in the car will be a part of the plan.
Heatstroke is an all too common scenario we see in Emergency Medicine. Warmer temperatures increase this risk, as do certain health conditions including respiratory problems and obesity. Patients who have been exposed to very high ambient temperatures, such as being locked in a hot car, are some of the most severely compromised patients we may see. Seizures, renal failure, heart arrhythmias, and death can result. Partially lowering the windows will not eliminate the risk.
So, if your dog will need to be left in the car unattended for any amount of time in the warmer weather, please reconsider and leave them at home. In addition to being dangerous, it is also illegal in the State of California. California Penal Code 597.7 PC prohibits leaving an animal (or animals) in an unattended vehicle, if by doing so you endanger the health or well-being of the animal. Under this law, conditions such as those listed below could subject you to criminal prosecution:
• the weather – heat or cold
• a lack of adequate ventilation
• a lack of food or water
• any other circumstance that could reasonably be expected to cause suffering, disability or death to the animal
A first-time conviction without major harm to the animal only subjects you to a maximum $100 fine per animal. However, if the animal does suffer great bodily injury, you face a misdemeanor, punishable by up to $500 and a maximum six-month county jail sentence.
So this summer, please, make sure your best buddy stays with you at all times, or make sure to leave them at home.