Once temperatures reach the 80's, you should hear the fan clutch engaging. Typically it will engage quiet frequently in city traffic, during highway travel it may engage every 30 minutes for a duration of several minutes.
Depending on the type of fan clutch (heavy duty versus light duty), the engine noise will change noticeably, also a slight loss in engine power will be experienced.
To check if the fan clutch is operating, rotate the fan blade by hand on a cold engine. If it spins freely, the fan clutch is completely dead.
If it resists spinning, the clutch is working, but may not be as efficient as it could be.
I replaced my fan clutch, because I had easy access. My old one was working, but the new one engages more often, which is telling me that it was due time to replace it.
Getting a fan clutch replaced while on the road, is an expensive undertaking.