My Dog is Cool
How Hot Do Cars Get?
Have you ever noticed how hot it can get inside a car on a summer day – far hotter than it is outside? That's because a car acts like a greenhouse, trapping the sun's heat.
A study by the Animal Protection Institute showed that even moderately warm temperatures outside can quickly lead to deadly temperatures inside a closed car.
The study, conducted during a local heat wave, compared an outside temperature of a shaded area with the inside of an automobile in three states: fully closed, with four windows cracked and with two windows cracked. Inside temperatures were measured with an indoor-outdoor thermometer and an oven thermometer (both readings are given).
Day 1 | |||
| Outside Temperature | Inside Closed Automobile | ||
| Indoor-Outdoor | Oven Thermometer | ||
9:00 am | 82°F / 27.8°C | 109°F / 42.8°C | ---- |
9:30 am | 87°F / 30.6°C | 115°F / 46.1°C | ---- |
10:00 am | 91°F / 32.8°C | 115°F / 46.1°C | ---- |
10:30 am | 94°F / 34.4°C | 114°F / 45.6°C | 115°F / 46.1°C |
11:00 am | 98°F / 36.7°C | 114°F / 45.6°C | 119°F / 48.3°C |
11:30 am | 100°F / 37.8°C | 117°F / 47.2°C | 124°F / 51.1°C |
12:00 pm | 101°F / 38.3°C | 119°F / 48.3°C | 127°F / 52.8°C |
1:30 pm | 112°F / 44.4°C | 124°F / 51.1°C | 130°F / 54.4°C |
2:30 pm | 125°F / 51.7°C | 130°F / 54.4°C | 159°F / 70.6°C |
4:00 pm | 98°F / 36.7°C | 110°F / 43.3°C | 110°F / 43.3°C |
Day 2 | |||
| Outside Temperature | Inside Auto – Four Windows Cracked | ||
| Indoor-Outdoor | Oven Thermometer | ||
9:15 am | 84°F / 28.9°C | 98°F / 36.7°C | 98°F / 36.7°C |
10:00 am | 88°F / 31.1°C | 103°F / 39.4°C | 105°F / 40.6°C |
10:30 am | 90°F / 32.2°C | 108°F / 42.2°C | 108°F / 42.2°C |
11:00 am | 92°F / 33.3°C | 109°F / 42.8°C | 109°F / 42.8°C |
12:00 pm | 95°F / 35.0°C | 113°F / 45.0°C | 113°F / 45.0°C |
1:00 pm | 101°F / 38.3°C | 114°F / 45.6°C | 115°F / 46.1°C |
2:00 pm | 110°F / 43.3°C | 123°F / 50.6°C | 120°F / 48.9°C |
3:40 pm | 112°F / 44.4°C | 129°F / 53.9°C | 128°F / 53.3°C |
4:00 pm | 115°F / 46.1°C | 132°F / 55.6°C | 130°F / 54.4°C |
Day 3 | |||
| Outside Temperature | Inside Auto – Two Windows Cracked | ||
| Indoor-Outdoor | Oven Thermometer | ||
8:30 am | 72°F / 22.2°C | 72°F / 22.2°C | 72°F / 22.2°C |
9:30 am | 80°F / 26.7°C | 95°F / 35.0°C | 95°F / 35.0°C |
12:00 pm | 88°F / 31.1°C | 105°F / 40.6°C | 105°F / 40.6°C |
1:50 pm | 99°F / 37.2°C | 109°F / 42.8°C | 109°F / 42.8°C |
2:30 pm | 104°F / 40.0°C | 120°F / 48.9°C | 120°F / 48.9°C |
| (both thermometers showed identical readings) | |||
Other studies show similar results:
- San Francisco State University – April 2007 fact sheet utilizing data from a Golden Gate Weather Services study.
- Another study reprinted from the Journal of the Louisiana State Medical Society.
- A study from Stanford University shows that even on comparatively cool days, such as 72°F (22.2°C), a car's internal temperature will rocket to 116°F (46.7°C) within 60 minutes. And keeping the windows open a crack hardly slows the rise at all.
© 2012 RedRover
Also, see:
- How Hot Does It Get in a Parked Car? – Dr. Ernie Ward
- Keep Pets Safe from Warm Weather
- How to Help Your Pet Survive the Summer Heat
- State Laws that Protect Animals Left in Parked Vehicles
- My Dog is Cool Pledge





