Leaving animals inside cars in warm weather can get risky for them very quickly.
Jan Null, a geoscientist at San Francisco State University, conducted a study of vehicle interiors in 2002 and again in 2004 when outside temperatures were between 72 and 96 degrees. On a 72-degree day, car interiors reached 91 degrees within 10 minutes. At 85 degrees outside, temperatures in the cars rose to 104 degrees within 10 minutes and to 119 within 30 minutes. At 95 degrees, temperatures rose to 119 within 15 minutes, peaking at over 140 within an hour. The darker the car's interior, the hotter it became. Further, cracking the windows 1½ to 2 inches was ineffective in reducing inside temperatures.
If you're traveling with pets in summer, experts say take steps to protect them:
Turn on the air conditioner to cool the interior of vehicle on warm days for 10 minutes before placing animals inside. Check that the back seat, where your pet will travel, is sufficiently cool.
Park in the shade during stops and remain with the animal.
If you're going on a long trip and will need food breaks, limit stops to drive-through restaurants when possible or eat at a place that will allow you to sit at a shady table outside with your pet.
Never leave animals unattended in the car in warm weather.
Give them plenty of water breaks.
Car air conditioning can shut off, so don't assume leaving your pet in the car with the air conditioner on will be OK.
Use see-through sun shades on the back and side windows to shield animals from the sun.
Cool the animal immediately with flowing water if it exhibits any heat-related symptoms, and seek immediate veterinary attention if the symptoms worsen.