If the search was not done within the same week or so, I don't think it would be too difficult for the defense to explain away. If the family owns a dog, perhaps he was wondering how long he could leave the dog in the car if they were going to be at a rest stop or something for a few minutes. I also don't understand why he would search for "how long does it take an animal to die in a hot car" instead of simply "animals in hot car". I bet there will be a lot more debate over this in a few months, with some arguing there is no way he would search for something so incriminating and unnecessary, so it might not be as clear cut as it looks.
If I want to know how long it takes for an animal to die in a hot car, that is what I am going to search for. Not animals in hot cars.