In dry mode, the fan speed is set to lowest possible. This allows the air to go over evaporator slowly causing water vapors in the air to become liquid. Also the compressor is turned on/off in short period of time. This keeps the evaporator cold enough for water vapor to become liquid while also keeping the room temperature to desired value.
I have personally tried this in Lahore that dry mode along with ceiling fan works best in humid weather like these days. Also i monitored the current consumption and it was less than running in cool mode at same set temperature. In humid days, temperature is not that high but the humidity levels make it uncomfortable so you can try this dry mode which makes room environment quite pleasant.