Yes humidity can make some peoples hair more greasy than others.
Whenever summer comes around and the humidity gets really high my hair tends to turn greasier than normal.
I find that applying some Tea Tree oil to my hair and washing my hair out with Apple Cider Vinegar helps to get rid of the greasy hair especially when it's more humid outside.
Eating A Balanced Diet of Healthy Fats and Carbs can also help with greasy hair.