What characteristic defines a rain-tight construction?

A rain-tight construction is specifically designed to prevent water from entering during heavy rain under certain specified conditions. This characteristic is crucial for protecting electrical installations and equipment from moisture damage, which can lead to electrical failures or hazards.

When discussing rain-tight construction, it's important to note that it does not imply an absolute barrier against all water exposure, as suggested in the first option. Rather, it focuses on maintaining integrity during significant rainfall. The idea of being water-resistant without being waterproof reflects the capacity to resist some level of moisture but not necessarily to withstand intense conditions, which aligns with the third option. Finally, while protective coverings may enhance moisture resistance, they are not a defining characteristic of rain-tight features, ruling out the necessity of such coverings for the designation of rain-tight construction.