Treinta y Tres: 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 Treinta y Tres the average yearly temperature is 22°C. During the hottest month, which in this case is January, the temperature can get up to 29°C. Instead the coldest month is July, reaching a minimum temperature of 15°C.