Why does hair take longer to dry after a shower on days with high relative humidity?

Because when there is higher humidity there are more water molecules in the air and so this leaves a lower capacity for water from your hair to evaporate. 

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen

Answerscripps institution of oceanography; i believe this is correct plz check first good luck;