Gotrice4

Situation: Hot, Humid summer day, temperatures in the upper 90's and humidity is 70%.
I go to start up my car and it starts to shake, not violently but noticeably. It's idling low and its lumpy I open the hood and rev it manually and goes away. My question is, is the heat and humidity causing the lumpy idle? I was thinking that maybe not enough oxygen is avaliable in the air. Or maybe what was stated b4 and maybe a not clean enough filter? any suggestions and insights would be greatly appreciated...thanks.