There's been a ton of very important coverage about the dangers of leaving your dogs in a hot car. Before you read the title and panic that I'm advocating for leaving your dog in the hot car on a hot day, stick with me while I explain.
Don't keep your dog locked in a hot car. It will very potentially lead to heat stroke and be potentially fatal. This has been hit on very hard in the past few years.
However, I am also here to tell you that there are in fact circumstances where crating out of your car (leaving your dog in your car for dog events) can be done safely in most (not all) temperatures.
At outdoor events like coursing, racing, some agility trials, some scent work/Nosework trials, etc there is no crating space inside the venue (sometimes because there is no interior space at all). In those cases you have a couple choices.
Option 1- set up crates outdoors
There are times when I opt to do this. At outdoor shows I will often opt to set up crates because the rings are often a long ways from the cars. Shows (when no COVID is around) tend to have more people entered and I am less comfortable leaving my dogs in the car in those scenarios.
When I do this I will either set up crate with water buckets or an xpen. Depending on the heat I may haul out battery powered fans or set up a canopy or sunshade cloth. The big downside to this is that your crates are very out in the open which means dogs are often very prone to barking as other dogs go past, they are accessible should someone with ill intents want to open their crates, and honestly it doesn't tend to be much cooler for the dogs. The setup in my picture isn't ideal for keeping dogs cool, usually I'd let them lay on the grass, but there were foxtails at that field and I was trying to keep them safe.
Option 2- crate out of your car with lots of cooling aides
There has been so much information about how this is never okay, this is bound to get some pushback from people outside dog sports. But within the dog world it's absolutely ubiquitous. Another thing that is absolutely ubiquitous at dog sport trials? The sun shade/aluminet. If you go to a trial where it is going to be even remotely warm, you will see people break out their sun shades to cover their windows, doors, and
entire cars. These wonderful inventions come in different densities and having sat in the car before I put a sunshade up and then after the temperature difference is marked. When I've been monitoring the temperature difference I've seen temperatures 10-15 degrees Fahrenheit lower than the air outside. These are very like the dashboard sunshades you'll see people use to keep their car warm and those are often also utilized at dog events as pictured to the left. On the far left of that picture you can also see the mesh window shades that I have for my front windows as well, which allow me to roll down my windows, but still have some time of shade and some slight barrier to reaching into my car. They add a bit of a cooling affect just like window tint does.
Another ubiquitous item you'll see at dog events are Ryobi fans. These are battery powered fans that you can use to create a nice cross breeze. Often people will bring chargers to charge their batteries at events or extra spares. I've found that my 18V 4.0Ah batteries will last me a full 8 hours on high and it's made a huge difference when I've had heavily coated dogs along with me. In moderately warm weather, I find the fans actually cool my desert dogs too much. In the picture you can note that I have both doors open to create a cross breeze and keep warm air from bottling up inside the car.
In that picture you can also note that Ash is still lying on a blanket and bed. It would be cooler for the dogs if I removed these, and some days, if it's warm enough, I will. There are cooler fabrics to lie on like Primo Pads. But if I really am worried about keeping my dogs cool (or if I have coated dogs along for the ride) I breaking out cooling mats. Check out Ollie utilizing one during a hot Fourth of July barbecue. Most dogs will naturally gravitate to them when they're overheating. Often with my desert sighthounds, they aren't at all interested in lying on one. There are lots of cooling mats on the market. Some of my favorites are the gel versions, though these do eventually heat up with the dog's body heat and you have to remove them to allow them to cool back down. There are also ice pack mats that you can utilize as well.
A few more cooling aides to consider: constant access to water buckets. You'll see in all my pictures of my dogs being crated in the car that there are always water buckets in their crates and those water buckets always have water. I will be honest, I don't always fill the water buckets for short trips to class and such, but during events those buckets always always have water. Additionally, in this picture you'll notice Ash's head and neck are wet. That is because prior to putting him back in his crate I put him in the kiddie pool the event had and hosed him down with water. When no kiddie pools are available something like a Hudson Sprayer with water is a great alternative. Finally in this picture, you'll notice he has a cooling coat on. Most (though not all) cooling coats work with evaporative cooling. You soak the jacket and that helps keep the dog cool. The two huge cautions with these types of cooling coats are that once they are dry your dog is now wearing a coat in hot weather and in a very humid enviornment the coat can actually make your dog warmer. When I use cooling coats with the dogs in crates they are always monitored closely.