When a vehicle is running hotter than normal but not yet overheating it can be caused by a few different things such as Clogged or damaged radiator, Low coolant level,l Damaged water pump or thermostat and even an Overworked engine.
Make sure that the coolant is clean and also make sure that your cooling fan is working properly.
If it's an electric cooling fan for the engine it should be running when the engine is hot and if it's an engine driven coolant fan it could be the fans bearings going bad not allowing it to spin properly which could prevent the engine from cooling down enough which could allow it to run hot but not hot enough to overheat.