The simple reason for this occurrence is the effect Evaporation and also the different factors affecting it.On the days of summer season, the temperature outside shoots up and the temperature is one of the factors that affects the rate of evaporation, higher the temperature higher will be the rate of evaporation. And as the rate of evaporation goes higher, the clothes get dried up quicker in the hot summer days, than in the winters and the monsoon. The humidity is another factor that affects the rate of evaporation (have an inversely proportional relation) and as the summer days are dry or have less humidity than the monsoon, the evaporation rate increases in the summer and decreases on monsoon. Thus letting the clothes dry faster in summers