The above answers are all good ones and if the engine is really running to hot you will notice a loss of power and possibly a smell of heated
oil. We have Summer temperatures of 110/115 degrees here with humidity and my engine was designed to run at 200/210 and it never gets above that unless I run into stop and gpo traffic after running at freeway speeds for a while. Also if you do change the thermostat many people drill a small hole in the flange to let a little water through until it warms up and opens.
Ron