Was your child OK? From what we’ve already learned here, that’s a dangerously long time to be trapped in a car under those ambient conditions.
WTF?
This is one of those things you’d swear somebody was making up. But I believe you…hence the WTF? squared to infinity and beyond…
Yes, forgot to mention that she was fine! She was obviously sweaty and hot but fine. In fact, she was singing the whole time she was in there. I, on the other hand, went into labor the next day!
You had a bun in the oven in more ways than one. 
You also learn to use something on your steering wheel to keep it from becoming untouchable. Best solution is windshield shades. I swear I’ve burned myself touching parts of my car after sitting in the LA Valley sun…
I’m a locksmith and I unlock cars for free 24x7x365 if there’s a child locked inside. Just about every other locksmith I know also has this same policy. There’s a big name locksmith franchise that advertises it right in their yellow pages ad.
However, that won’t be much help if the nearest locksmith is 30 miles away. Sorry I can’t help much with the timeline except to agree with what other posters have already said: pay attention to the child and see how they look.
It seem to me if a parent accidentally locks the kid in the car and runs inside the store to call a locksmith who is 5 minutes away and you the Impatient Samaritan break their window, you can expect to either write a check for $300 or give a $300 apology.
I grant they probably don’t fully realize the danger, as few people do. I thought I did before I read this thread.
But there is also a very practical point at work here, and I don’t think it should be vilified.
Let’s say I have perfect knowledge about this. I just locked my car keys and kid in my car, and it is 80 degrees out. So this very second, it is 80 degrees in that car. 80 degrees is not life-threatening.
According to the table above, in ten minutes it will reach 99 degrees in that car. Let’s assume that 99 degrees is life-threatening, but just barely. That means I have something like 8 minutes to figure out a way to solve this problem that won’t cost me $400 for a new window.
So I call the police and pop-a-lock and ask both “How fast can you get here and how much will it cost?”.
There is a world of difference between “Someone needs to do something about that now” and "Someone needs to do something about that* in the next five minutes*. When the best plan you’ve got is destructive and expensive, in the latter case you can try to come up with a better plan.
BUT
You must be prepared to drop your efforts to find a better plan and go with the plan at hand when you have run out of time.
That is exactly the gist and intent of the OP. I think this could be more readily addressed if we knew exactly what the first signs of serious trouble are.
Here in Arizona where during the summer, ambient frequently tops 110° it is a felony to leave a child or pet unattended in a car, locked or not. Every year there’s a sad story or two of someone who left the kid in the car in the driveway at home, killing them.
Well whaddya know—my second Threadspotting accolade. Thanks, Quartz. 
Have you ever heard of anybody ever being brought up on felony charges for a moment of forgetfulness that ended without incident? Say for example, a person pulls into their driveway and carries the groceries in without first removing the child/pet from the car, and a cop just happened to be driving by and witnessed it? Seems pretty Draconian to have a felony on your record for a minor lapse in judgement.
Do not expect to hear “You saved my baby! Thank you, thank you, thank you!” however.
One of my daughters was a lifeguard at the local pool for several summers. She did 2 or 3 saves a week. In most cases a) the saved child’s mom was chatting with other moms and didn’t notice her child was in trouble and b) the mom yelled at my daughter rather than saying “thank you.”
Human nature. Whatta ya gonna do?
This potato was left on dash of car while at work. Cooking thermometer reads 170F when I got off work. This would be a safe temperature for consumption of most meats, though it still left the potato a bit firm.
Bet it would fry an egg. Don’t know if it’s true (I could find out), but I was once told that the Rangers at Death Valley National Monument did (or still do) fry an egg on the sidewalk in the summer to demonstrate the magnitude of the intense heat there. Still, every year some clown goes hiking off in the desert without enough water and comes back in a body bag. No being in a hot car needed for that trick. When I lived in Zion NP I usually hiked alone, but whenever I hiked with other people I would invariably encounter the Giggle Factor when they discovered that I was carrying a gallon or even a gallon and a half of water, half of it frozen. Guess who ran out of water four miles from the trailhead in 95° heat?
Sadly, this year’s hot season has been especially brutal, and there’s been a spate of children being left in overheating locked cars and dying this hot season over here. One especially well-publicized case happened in a kindergarten van, the kid’s third day at school. From a fairly well-to-do family. Typically, the teachers all said it wasn’t their fault including the one who locked the van. Fortunately criminal charges have been filed.
I noticed a group of people around a car. I walked over.
The driver had accidently locked her baby in the car with the motor running and a window a small bit opened. The child was screaming and turning red, the driver was hysterical, and a man had a wire hanger through the window and was trying to unlock the door. The door lock was on the side of the inside handle.
Noticing the window opener was on the top of the handle, I asked without thinking “Wouldn’t it be easier to use a branch to press on the window opener to open the window, and open the door from the inside?”
It took about thirty seconds, the the poor driver thanked me about a million times. And the baby was okay.
The first summer I had my dog I was curious to see how long and at what temperature I could leave her in my vehicle just to run into a store or something. She was buckled into the back seat of my Jeep TJ with the two front windows down enough to stick her nose out - about 6 inches. It was 18C outside and sunny. I parked where I could see my vehicle from the store windows and timed it. As soon as I saw her look around worriedly and then climb down to curl up on the floor (where it’s cooler) I went out and we drove away.
It was 8 minutes.
Thank you for this. I read it when it first came out; the author richly deserved that Pulitzer.
On the lighter side… my aunt, who is a bit ditzy, once realized that she’d locked her baby in the car on a hot day, and called police at once. A cop arrived within a minutes, walked around the car with a thoughtful expression, and opened the door on the other side… which had been unlocked all along.
Whew!
Don’t tell me; let me guess—and she’s not even a real blonde, right? 
Ah, but she is!