Engine Heating

Hi;
1- My car heats up when driving in very hot weather with high speed.
2- I noticed even that it heats when I stop the car in a gas station for a few minutes in the highway. When I turn on the engine after a stopping in the middle of the high way, the temperature is shown as very high and gradually goes down within 2-3 seconds.
3- I also hear the high speed fan work at different temperatures, sometimes below 90 and some times above 90.
4- My car is a peugeot 307 that ran for 136,000 KM and is 6 years old and is regularly maintained at the Peugeot dealer workshop in Abu Dhabi.

Many Thanks