Boulder City has a high desert climate that swings hard between the seasons. Summer (June-September) is reliably hot — daytime highs over 40°C are normal in July and August — and the open trails around the dam and Lake Mead are dangerous in the afternoon. Walking and biking are best done at dawn or after sunset.
Spring (March-April) and autumn (October-November) are the best months to visit. Days are warm but bearable, nights are cool, and the desert is at its most photogenic. Winter is mild but cool — the wind off Lake Mead can be biting in January.