Every year, hundreds of pets die from heat exhaustion because they are left in parked vehicles. We've all heard the explanations: "Oh, it will just be a few minutes while I go into the store," or "But I cracked the windows..." These explanations don't amount to much if your pet becomes seriously ill or dies from being left in a vehicle.
The temperature inside your vehicle can rise almost 20º F in just 10 minutes, and almost 30º F in 20 minutes. The longer you wait, the higher it goes. At one hour, your vehicle's inside temperature can be more than 40 degrees higher than the outside temperature. Even on a 70-degree day, that's 110 degrees inside your vehicle!
Your vehicle can quickly reach a temperature that puts your pet at risk of serious illness and even death, even on a day that doesn't seem hot to you. And cracking the windows makes no difference.
Source: AVMA // avma.org/resources-tools/pet-owners/petcare/pets-vehicles