16v should run with a water temperature of 79-84c at the thermostat. The fan comes on at 85c at the radiator, but by that time the ECU thinks the water is at 99c. In stationary traffic in hot weather, the fan generally holds the temperature at 103c.
The gauge is not to be considered authoritative, but I won't worry at an indicated 100 in traffic, *if* it drops back once you're moving. On the NA, the oil and water are at close to the same temperature due to the intercooler behind the filter, so that's another clue; again, expect 90-100c.