If your sitting in traffic, the water temperature will rise. When your moving, the air damn underneath the car deflects air through your radiator. The ECM wont kick on the fans untill the water temp reaches around 220* or so ... I think. Someone here will have the right degree....
Turning on the A/C will kick on the fans, or if you feel up to it, wire this up
http://www.xious.com/camaro/install-fanswitch.html
If you dont feel confident to do that, slp sells a manual fan switch for like 70 bucks. It expensive, but thats SLP for ya