If a leak is difficult to find enlist a helper and go up on the roof with a garden hose.
Roof leaking bottom window.
Make sure the sill at the bottom of the window frame is pitched.
Have a roofing expert conduct an inspection of your roof system.
Isolate areas when you run the hose.
Unfortunately this may not be the case for water leaking from the bottom.
Remove damaged exterior caulking clean the window frame and recaulk.
Window leaks can result from a structural failing elsewhere in the home such as an opening in the roof upper floors or siding.
The problem is often with the window itself instead of anything that you might be able to do to prevent water from coming in.
Check the gasket between the window frame and the glass.
Re seal the glass to the gasket with clear silicone caulk.
Sometimes leaking water is finding its way into your through your window sills or frame but is actually coming from your roof.
You can try some simple maintenance work such as.
Missing shingles or a failing roof system might be your culprit.
Start low soaking the area just above where the leak appears in the house.
If you notice water stains on the wall above the window or along the top or bottom of the frame this usually means there is a leak inside the walls.
Recaulk the corner flashing if any areas have hardened caulk.
For example soak the downhill side of a chimney first then each side then the top on both sides.