If there is decent airflow through the radiator then the bike should sit at/near the thermostat opening point of 78-80C or 176F irrespective of the ambient temperature. When you get stuck in traffic (no air passing through the radiator) the temperature will rise to around 100 (212) and should cycle up/down as the fans switch on off. To get higher than that would suggest maybe the fans don't work or the thermostat is stuck.
Let's assume the cooling system is full and the reservoir has a decent volume as well (you checked that, right?).
If the radiator stays cold when the engine starts and then suddenly gets too hot to touch around 176, the thermostat probably works. If the radiator gently warms up as soon as the engine starts, the thermostat is probably jammed half-open. If the radiator never gets hot, the thermostat is probably jammed shut.
Check the fan switches itself on around 212F and off a few degrees below that.
Some have altered the fan wiring to put a manual bypass switch in place, so if you are going to get mired in traffic you can start the fan earlier.