Hot car safety: how fast does a car heat up with a child inside?

Concerns & risks

You nearly left a sleeping toddler in the car on a mild day, thinking cracked windows would be enough.

Causes & evidence

NHTSA says vehicles can heat up very quickly, with temperatures rising about 20 degrees in as little as 10 minutes. An outside temperature in the mid-60s can push the inside of a car above 110°F. Children's bodies warm three to five times faster than adults' bodies, and heatstroke begins when core body temperature reaches about 104°F; a core temperature of about 107°F is lethal. Cracking the windows or parking in the shade does little to help. NHTSA reports that more than 1,000 children have died in hot cars since 1998, and that over half of these deaths happen when a parent or caregiver forgets a child is in the car. Others happen when children climb into an unlocked vehicle. NHTSA's advice is to never leave a child alone in a vehicle for any length of time.

Edge cases: heatstroke can happen on cool, sunny days and at any time of year, not just in summer or in hot states. Trunks are also dangerous, so teach children that cars and trunks are not play areas. Many states have laws protecting bystanders who break into a car to rescue a child, but rules vary; the safest first step is always to call 911.

Believing it won't happen to you is the biggest risk. NHTSA notes that changes in routine and tired caregivers are common factors.

What to do

1. Make it a rule: a child never stays in the car alone, even for a minute.
2. Put your bag, phone or work badge in the back seat when a child is with you.
3. Ask your childcare provider to call if your child doesn't arrive as expected.
4. Lock your car at home and keep keys away from children.
5. If you see a child alone in a car, call 911 right away.

Common mistakes:

• Thinking cracked windows keep a car cool
• Leaving a sleeping child 'just for a minute'
• Leaving the car unlocked in the driveway

ReportSpeedMan tip: Many newer cars have a rear-seat reminder. Check your manual to see whether it's on, but keep your own back-seat habit too.

What I would actually do

I'd put my work bag on the floor behind the driver's seat every single time my child rides with me, so I can't leave without looking back.

The trade-off people miss: the risk is highest on unusual days, such as when the other parent normally does drop-off. Those are the days a routine fails, so add a phone reminder for them.

Proof that it worked

Checking the back seat is automatic every time you park.

Quick FAQ

Is it okay if the engine and A/C are running?
NHTSA says never leave a child alone in a vehicle for any reason.

What if I see a child alone in a car?
Call 911 right away.

Do rear-seat reminders work?
They help, but keep your own habit too.

Wrap-up: A car can heat up about 20 degrees in 10 minutes, and children heat up far faster than adults. Never leave a child alone in a car, and build a back-seat check habit.

Wiki: Vehicle Recalls and Kids and Screen Time.

Hot car safety: official pages behind this answer

• NHTSA: Child heatstroke prevention
• NHTSA: Child safety