Car Overheating

2003 Crown Victoria
82,000 miles

When parked with the air conditioner on I can see the temperature rise till it hits the danger zone. If I am driving I have no problems with the temperature.
I have flushed the radiator and it is full. I have replaced the thermostat. There is no leaks and no fluid coming from the weep hole of the water pump and the fan is running.
Any thoughts on what I should replace next?

Check to be sure the cooling fans are operating correctly. There should be 2 speeds on the fan. Sounds like the fans are not coming on. As you drive down the road, there is enough air flowing through the radiator to keep it from overheating.