Most aluminum doors and windows are rated for 1) thermal transmission, 2) structural strength, 3) air infiltration, 4) security, and 5) water infiltration. In the water infiltration test, most older aluminum sliding patio doors rated very poorly or not at all. Those doors were often sold without notification that they should be installed only in "protected" locations. That is, locations that were not exposed to direct water (such as rain).
Your best bet is to install a canopy, or awning to protect the door from the rain or to install a new sliding door that has a water infiltration rating of somewhere between 5 and 10 PSF (pouds per square foot). This roughly equates to a 25 to 50 MPH wind pushing the water through. The building code in your area has a maximum wind speed for building design. Find out what that wind speed is and ask your door supplier to provide models that will prevent water infiltration at that level. If your door is new and has a water infiltration rating, call the installer to check for possible problems with the seals or installation.