Sliding windows have part of their track exposed to the weather. There is no way water does not get in there and why the weep holes were put in and why it's very important to keep them clean. Water won't be the only issue...bugs, dirt, bits of leaves, etc. also collect there. In extremely heavy rain or under heavy hose pressure the weep holes sometimes do not drain the track fast enough...overflow can then happen.
In our dusty region I brush, then vacuum out track dirt, use a pipe cleaner &/or toothpicks to clean all holes monthly. 2nd step...use a squirt bottle set on "stream" to wash out the tracks and holes to be sure they allow water to drain. If they don't keep picking out the holes in case debris still exits. This can be done from the inside if you also remove the screen, open the window and can lean out and reach the weep holes--then you don't have to keep going from outside to inside to do the job. For the 3rd step I will lightly wipe the track rails with a light lubricant for ease of window opening.
It is indeed possible the sealant around your windows has weather and no longer sealing. You'll need to remove the old sealant, clean the area to remove residue then reapply the appropriate type of sealant. Of course that will require a few dry days.;) For a quick fix you can try to dry off the area as well as possible and apply Gorilla Tape around the window where it's leaking. It will leave a sticky residue but if you are going to reseal a window later it will need to be cleaned anyway. The important thing is to stop the water from getting inside to the interior or down into the wall structure causing mold and rot.
