Car

This may sound really strange, but if it rains during the night and I go to start my car in the a.M it almost wants to stall and I do not get the power that I should the check engine light also flashes. Once I drive the car on a straight away without stopping (at this point I have to keep pressing the gas peddle up and down)the light stops flashing and the car is fine. This does not happen if I am driving already and it starts to rain it only happens when the car is sitting over night without being started. Could this possible be some sort of oxygen sensor? I am totally out of ideas on what might be causing this. Please help. P.S. I would like to give a big thanks to everyone that helps people like me with these issues!