2008 NEC 406.8
406.8 Receptacles in Damp or Wet Locations.
(A) Damp Locations: A receptacle installed outdoors in a location protected from the weather or in other damp locations shall have an enclosure for the receptacle that is weatherproof when the receptacle is covered (attachments plug cap not inserted and receptacle covers closed).
An installation suitable for wet locations shall also be considered suitable for damp locations.
A receptacle shall be considered to be in a location protected from the weather where located under roofed open porches, canopies, marquees, and the like, and will not be subjected to a beating rain or water runoff. All 15- and 20-ampree, 125- and 250-volt non-locking receptacles shall be a listed weather-resistant type.
(B) Wet Locations.
(1) 15- and 20- ampere Receptacle in Wet Location.
15-And 20- ampere, 125- and 250- volt receptacle installed in a wet location shall have an enclosure that is weatherproof whether of not the attachment plug cap in inserted. All 15- and 20-ampree, 125- and 250-volt non-locking receptacles shall be a listed weather-resistant type.
