sun effecting signal is for satDid You, by any chance, Contact Your ISP and see if They were doing any Maint...?!? Sometimes a Tree Limb will fall on the lines or even a car might hit a pole... Doesn't hurt to ask...?!?
Saw in another post about the Position of the Sun effecting the signal, if Your ISP is in a Building that has those Big Sat Dishes outside You could experience fluctuation in signal as the Earth changes It's Position Twice a Year, just a Thought...!