Generally the boiling point of water is 100 degree centigrade but in summer the water evaporates in small temperatures.why?

The concept here would be explained through the average velocity of the atoms which gets collided to each other wth some distinct abnormal velocity. In summer at some temperature some of the atoms of the molecules strikes woith another with this avg. speed and transfer that energy to the other say third atom and this third atom may spped up more as acompare to previous one from which it collided and so on the prcoess continues. And hence, the water resulted in evaporation during summer too at this small temperatures.