I live in Dallas, Texas and the ambient air temperature this morning was 89 degrees @ 6:00am. The ambient air temperature this afternoon at 3:00pm in heavy traffic was 104 degrees.
The specs on my Jeep are;
Model: Cherokee Sport (XJ)
Engine: 4.0L inline 6
Transmission: AW-4 Automatic (4 speed with overdrive)
Transfer Case: New Process 231J with SYE
Lift Kit: Rubicon Express 4.5 short arm
Tires: Goodyear 32x11.50x15
Wheels: Cragar 15x8 - 3.75backspacing with 5x4.5 bolt pattern
My XJ has 230400 miles on the odometer.
At ambient air temperatures below 90 degrees the temperature gauge reads 210 degrees and has no problems at all. When the ambient air temperature gets above 100 degrees and my air conditioner is turned on the temperature gauge slowly creeps up and over 210 to 220 then spikes up to 250 and then the "Check Gauge" red warning light turns on.
NOTE: As of this date almost everything on my jeep has been changed out, including the engine. I hope to help you avoid spending the money and time that I have spent to fix your overheating vehicle. Good luck and remember to walk away and think when you have done everything you can think of to fix your vehicle and nothing seems to be working. :)