[olddog]

Humidity only affects things that are using evaporation to cool. Like people and industrial evaporative cooling towers. So, the humidity has little affect on a car's radiator.

Are you sure the thermostat is working correctly?

Radiator big enough?

Good air flow through radiator?

Water pump moving enough water?

One or a combination of these has to be the culprit.

220 is getting warm, but 200 would not bother me.