Las Vegas monsoon storms from July through September can drop one to two inches of rain in under an hour, overwhelming flat-roof drainage and forcing water beneath improperly sealed flashings. Extreme temperature swings — above 100°F in summer to freezing in winter — also stress supply lines in the valley's large inventory of 1980s and 1990s construction.
Polybutylene supply piping, widely installed during that building boom and known to fail without warning, remains in a meaningful share of Las Vegas homes. A single second-floor line failure can flood multiple stories before you return home.
Nevada homeowners policies cover sudden, accidental plumbing failures but not monsoon runoff flooding — that requires a separate NFIP or private flood policy. Ask your contractor for daily psychrometric drying logs, which Nevada insurers require to process water damage claims.