Question

wet clothes do not dry easily on rainy days

Answer 1

Because in rainy days there is no sunlight

Answer 2

We know that evaporation is directly proprtional to the temperature and inversely proprtional to the moisture content in the surroundings.
Thus as on a rainy day the moisture content is high therefore the rate of evaporation of water from the clothes is much slower and also the temperature is a bit lowered. Hence wet clothes do not dry easily on a rainy day.