This week, PETA honored Wisconsin's Outagamie County Highway Department for a roadside rescue that unfolded on May 27, the hottest day of the year up to that point.

The crew had pulled up to a park-and-ride in Little Chute for a routine mowing job. Before they started, seasonal worker Dakota DeWilde, only a few weeks into the job, caught an odd, litter-box-like smell coming from a van that had been sitting there for days.

He peered inside and found a black kitten staring back at him through the window, along with at least a dozen cats and kittens trapped in sweltering conditions. The older cats were already panting and lethargic; some didn't even lift their heads.

The van had been flagged as abandoned for about a week. Rather than force their way in, the crew waited for law enforcement to grant permission.

Once an officer gave the go-ahead, they opened the rear door, loaded the animals into a carrier they found nearby, and rushed all 12 cats to the Fox Valley Humane Association. Many have since been adopted.

In recognition of the team's quick thinking, PETA presented the department with its Compassionate Action Award.

The case is a stark reminder of how fast a parked vehicle can become a furnace, a danger to pets and people alike.

(MORE: Meteorologist explains the scary science of a hot car)

The numbers are sobering. On a 90-degree day like this one, the inside of a parked car can hit 109 degrees in just 10 minutes, blow past 119 degrees within 20, and reach roughly 124 degrees in half an hour. Cracking the windows barely slows the climb.

Cars heat up fastest in those first few minutes, which is exactly what makes the danger so easy to underestimate.

Dogs and cats are especially vulnerable because they can't cool down as efficiently as people. They rely mostly on panting to regulate their body temperature.

When that system is overwhelmed, an animal's temperature can rise to the point of irreversible organ damage or death. That's why experts urge owners never to leave animals in parked vehicles, and to call for help immediately if they spot one in distress.