According To The Humane Society of The United States

"Common sense tells most people that leaving their pet inside a parked vehicle on a hot, summer day could be dangerous after an extended period of time. But most people don't realize that the temperature can skyrocket after just a few minutes. Parking in the shade or leaving the windows cracked does little to alleviate this pressure cooker.

On a warm, sunny day windows collect light, trapping heat inside the vehicle, and pushing the temperature inside to dangerous levels. On an 85-degree Fahrenheit day, for example, the temperature inside a car with the windows opened slightly can reach 102 degrees within ten minutes. After 30 minutes, the temperature will reach 120 degrees. At 110 degrees, pets are in danger of heatstroke. On hot and humid days, the temperature in a car parked in direct sunlight can rise more than 30 degrees per minute, and quickly become lethal.

A recent study by the Stanford University School of Medicine showed that temperatures inside cars can rise dramatically even on mild days. With outside temperatures as low as 72 degrees, researchers found that a car's interior temperature can heat up by an average of 40 degrees within an hour, with 80% of that increase in the first 30 minutes. A cracked window provides little relief from this oven effect. The Stanford researchers found that a cracked window had an insignificant effect on both the rate of heating and the final temperature after an hour.

Pets, more so than humans, are susceptible to overheating. While people can roll down windows, turn on the air conditioner or exit the vehicle when they become too hot, pets cannot. And pets are much less efficient at cooling themselves than people are.

Dogs, for example, are designed to conserve heat. Their sweat glands, which exist on their nose and the pads of their feet, are inadequate for cooling during hot days. Panting and drinking water helps cool them, but if they only have overheated air to breathe, dogs can suffer brain and organ damage after just 15 minutes. Short-nosed breeds, like pugs and bulldogs, young pets, seniors or pets with weight, respiratory, cardiovascular or other health problems are especially susceptible to heat-related stress."

And to refresh yourself...try keeping a carafe of water (with sliced cucumbers) in the fridge. It is delightful on these HOT summer days.