To stop chasing leaks around and wondering about advice, my suggestion is to run the hose around that side of the house and see if you get water in the sill area. Then start to remove siding and see where it is coming from. Remember, to find a leak you need to be the water...it goes anywhere downhill always.
Basically do not tuck your raincoat into your pants or you get wet shoes.
Then you will know exactly what you need to do to stop the water.
If no water comes in, then you have a sill issue when it freezes, I have seen it before when there is no sill seal.