The gutters are clear and the patio is level.
Patio door leaking at top.
Door bottoms seal between the panel and door sill so watch for signs when your door bottom needs replacing.
Have a reputable sliding door contractor remove the door if it has not been damaged build a new frame and reinstall the door.
Spray the door and look for the leak location.
It may seem obvious but a door left open or one that cannot be closed tightly because of wear and tear is a significant problem during a storm.
I plan to seal.
Aim a garden water hose with a sprayer set on mist or low at the outside of the sliding door.
Causes of door leaks there are many potential pathways for water to leak in through a door but the biggest opening is of course the doorway itself.
Door bottoms are important but leaks can also be caused by the door sill.
There are patio doors to the balcony and the leak comes in under the wooden frame of the patio doors the doors are plastic and soaks the carpet and woodwork.
Even brand new door bottoms won t create a secure seal if your door sill isn t properly adjusted.
A sliding glass door is no better than the frame into which it is placed.
It just comes in in one corner.
If you cannot re create the leak problem inspect the interior of the door for stains or rust.
If a frame is crooked water can leak into the gaps between door and frame.
Damage to the door itself.
Test the door for the location of the leak.