It's a quick stop on Main Street, or a fast dash into a shop before an appointment — "I'll only be a minute." That minute is exactly how a lot of dogs end up in trouble every summer. Missouri heat and humidity make a parked car dangerous a lot faster than most owners expect, and it's one of those risks that's easy to underestimate until you've seen the numbers.
How Fast a Car Actually Heats Up
According to the American Veterinary Medical Association, the temperature inside a parked car can climb almost 20°F in just 10 minutes, and nearly 30°F within 20 minutes. Give it an hour, and the interior can be more than 40 degrees hotter than the air outside. On a mild 70-degree day, that math still lands well over 110°F inside the car. Cracking the windows doesn't meaningfully slow this down — the AVMA is clear that it isn't an effective fix.
A dog's normal body temperature sits around 101.5–102.2°F. It doesn't take much of a climb above that before things get serious, which is why even a "quick errand" isn't worth the risk here in St. Charles once the summer heat and humidity settle in.
Some Dogs Have Even Less Margin
Every dog is vulnerable in a hot car, but some have less room for error. Short-nosed (brachycephalic) breeds like French Bulldogs, Bulldogs, Pugs, and Boston Terriers can't pant as efficiently to cool themselves, so heat builds up faster. Senior dogs, puppies, overweight dogs, and dogs with heart or respiratory conditions are also at higher risk. And heavily coated or matted dogs run hotter too — a coat that's supposed to help regulate body temperature can't do that job well once it's packed down and matted, which just traps heat closer to the skin instead of letting air move through it.
Where Grooming Actually Fits Into This
This is where our end of things comes in. According to the American Kennel Club, regular brushing removes dead undercoat and lets air circulate against the skin, which helps a dog regulate its own temperature through the summer — brushing out mats and trimming excess hair around the legs and belly helps too. That's a big part of why we keep pushing regular brush-outs for our doodle and heavy-coated clients all summer (something we get into more in our post on why doodles mat so fast in Missouri humidity). It's also why shaving a true double coat down to the skin usually backfires and makes a dog hotter, not cooler, once that natural insulating layer is gone — we cover the reasoning in our post on double-coated dogs and summer shaving.
We keep this in mind with our own dogs too. Belle, our Weimaraner, has a short, dense coat, and she still gets extra brush-outs through peak summer just to keep things moving and air flowing against her skin. A well-maintained coat won't undo the danger of a hot car, but it does mean a dog starts from a better place on an already-hot day — on a walk, in the yard, or waiting in a car they should never be waiting in to begin with.
The Simplest Rule
If your dog can't come inside with you, the car isn't a safe place to leave them — not for a five-minute stop on Main Street, not with the windows cracked, not parked in the shade. St. Charles gets plenty of hot, sticky stretches all summer, and "just a minute" has a way of turning into ten. If you're headed somewhere your dog can't come along, it's simpler and safer to leave them at home.
Signs of Overheating to Watch For
Whether it's a car, a walk, or just a hot afternoon in the yard, it helps to know what overheating looks like. Watch for heavy, non-stop panting, excessive drooling, restlessness, weakness, wobbliness, vomiting, or collapse. If you see any of that, get your dog into shade or air conditioning right away, offer water, and call your vet or an emergency vet immediately — heatstroke can escalate fast, and it isn't something to try to manage at home. This is guidance, not a diagnosis; if you're ever unsure how serious it is, treat it as an emergency and let your vet make that call.
Regular grooming is one of the easiest ways to help your dog handle a Missouri summer, and it's something we can help with all season. Book an appointment here and we'll take care of the coat side of things.
Frequently Asked Questions
How hot does it really get inside a parked car?
Fast. The AVMA reports interior temperatures can rise almost 20°F in 10 minutes and nearly 30°F in 20 minutes, meaning even a 70-degree day can turn into a 110+ degree car within a short stop.
Does cracking the windows help?
Not meaningfully. The AVMA specifically notes that cracked windows don't prevent the dangerous temperature climb inside a parked car.
Are some dogs more at risk than others?
Yes. Short-nosed breeds, seniors, puppies, overweight dogs, dogs with heart or breathing conditions, and heavily coated or matted dogs all have less margin for error in the heat.
Can a matted coat actually make a dog hotter?
Yes — a matted coat can't do its job of regulating body temperature the way a well-brushed one can, which traps heat closer to the skin instead of allowing airflow.
What should I do if I think my dog is overheating?
Get them into shade or air conditioning, offer water, and contact your vet or an emergency vet right away. Heatstroke can progress quickly, so treat it as an emergency rather than something to wait out.
What's the safest rule of thumb?
If your dog can't come inside with you, don't bring them along for that stop. It's simpler and safer to leave them at home than to leave them in the car for even a few minutes.