Water Problem on Patio
I'm sure the water is from "ground water". That is to say, it's from the water table being pushed up from the adjacent hillside. During the wet season, hillsides get saturated and will cause lower level water tables to rise. 

An easy fix is to add a "french drain" between your patio and the hillside. Just dig a trench about 8" to 12" below the bottom of the patio slab. Install a 3" perforated pipe on about 3" of gravel (drain rock, not crushed rock, because you want water to flow through the rock and enter the perf pipe.) Then fill up the trench with more rock. (If you want it to last longer, you could line the trench...bottom, sides and top...with filter fabric.) Make sure you "daylight" the end of the perf pipe. That is to say, extend the pipe to a location that will allow the water to run out. Make sure the pipe is level or slopes down to the exit slightly. 

The reason you are experiencing this now is because something has changed. Somebody uphill from you has changed a waterway or diverted some water towards you...