Milford Sound: are you wondering about the weather you might find during your holiday? Befor organizing a holiday we always think about the wheather we might find when we get there. In Milford Sound the average yearly temperature is 10°C. During the hottest month, which in this case is January, the temperature can get up to 15°C and the temperature of the sea reaches 14°C. Instead the coldest month is July, reaching a minimum temperature of 6°C. Here instead the water temperature drops to 10°C.