Hot car dog temperature calculator

How hot does a car get in the sun?

Hotter than most people expect, and faster. In 2002, researchers from Stanford University and San Francisco State University parked a dark-blue sedan in full sun on 16 clear days, with outside temperatures from 72 to 96°F (22 to 36°C), and logged the temperature inside every 5 minutes for an hour. The results were published in Pediatrics in 2005, and the rate of heating was the same whatever the outside temperature:

• The inside warmed by an average of 3.2°F every 5 minutes over the hour.
• 80% of the rise happened in the first 30 minutes.
• After an hour the car was on average about 40°F (22°C) hotter than outside.
• Even on the coolest day, 72°F (22°C), the inside reached 117°F (47°C).

The calculator uses the study's average rise at each point in time, as summarized by co-author Jan Null:

10 min: +19°F · 20 min: +29°F · 30 min: +34°F · 60 min: +43°F

Between those points it draws a straight line. Cars heat fastest at the start, so the real figure in between may be a little higher.

Hot car temperature chart

Estimated temperature inside a car parked in the sun, from the outside temperature and how long it has been parked.

The Merck Veterinary Manual gives a similar picture: on an 85°F (29°C) day the inside of a car can pass 100°F (38°C) in 10 minutes and 120°F (49°C) in 35 minutes.

Does cracking the windows help?

Not in any way that matters. On two of the test days the researchers repeated the hour with the windows open 1.5 inches (4 cm). The heating rates with the windows cracked and closed were 3.1 and 3.4°F per 5 minutes, a difference that wasn't statistically meaningful, and the final temperature was identical. Merck adds that parking in the shade doesn't necessarily make a car safe either. Pre-cooling with air conditioning buys only about 5 minutes: in the study's trial runs the car was back at the outside temperature within 5 minutes of the AC being turned off.

Why a hot car is so dangerous for dogs

Dogs rely heavily on panting to shed heat, and a closed car soon gets hotter than a dog's own body (see normal readings in our dog temperature checker), so the air heats the dog instead of cooling it. On the Tufts weather safety scale, which scores the risk of the temperature a dog is exposed to, a medium or large dog with no water or shade reaches the potentially life-threatening level from about 83°F (28°C). In the calculator, a sunny car reaches that within minutes on all but cold days.

Hot cars are not the most common cause of heatstroke: a UK study of over 900,000 dogs found they caused about 5% of cases with a known cause, against 74% for exercise. But dogs that overheated in cars had similar odds of dying as dogs that overheated during exercise. Our is it too hot to walk my dog? checker covers the walk side.

What to do if a dog overheats in a car

Signs of heatstroke include skin that is hot to the touch, vomiting, drooling, rapid panting, distress, loss of coordination, collapse and unconsciousness. If it's your dog:

1. Get the dog out of the car and into shade or air conditioning.
2. Cool it gradually: hose it down with cool (not cold) water and use ice packs, wet towels and a fan. Never submerge it in cold water.
3. Drive to the nearest vet straight away, phoning ahead so they are ready.

If it's someone else's dog in distress, call local animal control or the police. Laws on breaking into a car to rescue an animal differ from state to state. Planning a road trip? Our dog travel checklist builds in rest stops so your dog is never left waiting in the car.