All 15- and 20-ampere receptacles, rated 125 and 250 volts, with straight blades, installed in damp and wet locations must be a listed weather-resistant type.

Currently, standard 15- and -20 ampere receptacles installed in damp and wet locations are protected from the weather by weatherproof enclosures or weatherproof covers. Unfortunately, poor installation or assembly practices have often allowed water into the enclosure and damaged the receptacle. For a number of reasons, outdoor receptacles are subject to harsher conditions than indoor receptacles. A NEMA/UL study found the failure rate of GFCI receptacles installed outdoors was more than double the failure rate in other locations.