Thanks for the suggestions, The radiator/overflow tank level is ok. I agree, a good flushing, changing the coolant and thermostat is a good first step.
I bought the jeep 2 years ago, and just got the AC working, so the additional tempature load is new to my summer driving, and I have no service records as to coolant maintenance. The coolant is clean, still green, no sign of rust or lumps,hopefully the radiator isn't too clogged up.