Yes, it is extremely hot and just like extreme cold extreme hot is hard on your vehicle. The extreme heat will make your vehicle reveal its weaknesses. The extreme heat will create problems.
When the mercury climbs the tow trucks start to frequent the auto repair shops just like a winter freeze.
Automobiles are designed to survive under temperature extremes but many times you, the owner, subject your vehicle to situations where those extremes are exceeded.
The temperature in your vehicle when parked with the windows rolled up in direct sunlight can exceed some of the design parameters. Leaving some windows cracked open can alleviate that problem. Having one of those windshield sun shades will greatly reduce the temperature inside your vehicle.
For many of you summer is vacation season. Time to hook up the trailer or boat, maybe put the camper on the truck, stuff a Thule box full of camping gear on top or maybe all of the above. Be careful, you may be overloading your vehicle. Your vehicle has a load limit and the limit is lower than you think. A passenger equals only 150 lbs (68 kg). I am significantly more than one passenger.
Canoes, kayaks, car top boxes all add weight that must be counted. On top of that they increase drag. Your vehicle needs to work harder just moving through the air.
An overloaded vehicle climbing a mountain pass at three in the afternoon on a 30 degree Celsius day is going to exceed the engineers’ design parameters. Sure, you made it to the top without overheating but the damage that is done may not be evident immediately. The temperature gauge is likely only reporting engine coolant temperature. There are a bunch of other fluids involved in keeping parts properly lubricated and functioning.
Engine oil, transmission fluid, and gear oil all have temperature and load limits. Most vehicles do not turn on a light when the transmission oil gets too hot, nor when the engine oil gets too hot. Other than race cars you definitely won’t have a gauge for your differential oil.
When lubricants such as these get too hot they oxidize. Oxidation ruins their lubrication properties and moving stuff begins to wear. Failure of moving parts will not be catastrophic but will rapidly increase. Instead of a 200 000 km overhaul your transmission will request that same service at possibly 100 000 km.
If towing season was hot and your vehicle was really loaded consider replacing all these fluids as soon as you get home.
When possible do your traveling in the early morning or the evening when temperatures are down. Spend the hot part of the day at the beach.