8.1 Engine Running Hot

I arrived in Little Rock Sunday afternoon after a 344 mile run from Nashville. Started driving at 5:30am, outside temps were 63 deg and initially I again ran with the engine compt door open. My highway speed was 62mph. About 10:00am I decided to try something different. I shut the engine compt door; outside temps had climbed to 74 deg and during this period of driving reached the mid-80's. My engine temp stayed in the normal mid-range range as indicated on the temp gauge. At different times, the engine temp would climb 1 or 2 graduations on the gauge and then slowly come back to the normal area on the gauge. I maintained a constant 62mph. So at this point, I don't know if my thermostat was previously stuck and then cleared or if there was/is something going on with my fan clutch. In the past, I have heard the fan "roar" when it cut in at idle. I can't say I have heard it on this trip since last Friday. I do think its detrimental to engine cooling to run with the engine compt door open, because while I do have natural cooling (free flow air) to the engine, the fan clutch will not sense a heat buildup in the compt and probably will not cut in.
As a minimum, I will have my thermostat replaced as it is still original and the spring may be getting weak.
I did not get my original water pump returned, but I will retrieve it upon my return to VA.
So, I don't know if my problem is resolved, I will know more when I start heading east on Sunday; either toward SC or home to VA, depending what happens with the hurricane threatening the east coast. This forum has been great with all the commenting posts. I appreciate it.