Water leak in glass seal at the bottom of the window.

If it's condensation, you should see it in other places, like other windows or cold spots. Look carefully. A dehumidifier never hurts during extensive use, especially in humid areas.

If no other signs of condensation, you do likely have a window leak. Make sure the weep holes are completely clear. Then spray with a hose above the window, and from all sides, and check which location produces a leak. It could be leaking around the top and running down inside.