I agree the most likely cause is a leaking roof. When my roof has leaked the water has come out the windows/basement as it runs down the insides of the walls.

OP, if you can get on a ladder and take a look at the roof in the general area(s) you're seeing water, it might be obvious where the water is coming in, or it might not, but it's a good place to start. (Common causes include ice dams, missing shingles, leaking around things coming out of the roof like exhausts or vents, leaking around things attached to the roof like guy wires or satellite dishes).