more airflow over the radiator keeps it cool on the highway, in town more sitting in traffic and lower speeds let it run hotter.
If it is nearly over heating start with the easy things check the radiator fluid. if it is full then it is probably the thermostat sticking either open or closed. since it runs cooler on the highway I would think it is stuck open allowing the water to circulate through the radiator.
The 2003 Jeep Grand-Cherokee runs on regular unleaded.
The 2014 Jeep Cherokee runs on regular unleaded.
The 2001 Jeep Cherokee runs on regular unleaded.
The 2010 Jeep Grand-Cherokee runs on regular unleaded.
The 2009 Jeep Grand-Cherokee runs on regular unleaded.
The 2007 Jeep Grand-Cherokee runs on regular unleaded.
The 2004 Jeep Grand-Cherokee runs on regular unleaded.
The 2006 Jeep Grand-Cherokee runs on regular unleaded.
The 2014 Jeep Grand-Cherokee runs on flex-fuel (FFV).
The 2012 Jeep Grand-Cherokee runs on flex-fuel (FFV).
The 2013 Jeep Grand-Cherokee runs on flex-fuel (unleaded/E85).
The 2003 Jeep Wrangler runs on regular unleaded.