Spring (March-May): Widely considered the best season to visit - warm, dry days (20-30°C) without the extreme summer heat, ideal for both Strip exploring and desert day trips like Red Rock Canyon and Valley of Fire. Spring break weeks bring bigger crowds and higher hotel rates.
Summer (June-August): Brutally hot, with daytime highs regularly exceeding 40°C and sometimes topping 45°C. Pool culture and air-conditioned casinos make the heat manageable if you plan around it, and hotel rates can actually be lower midweek due to reduced demand, but outdoor day trips (Death Valley especially) require serious caution.
Autumn (September-November): Temperatures cool back into the comfortable 20-30°C range by October, crowds thin after Labor Day, and it's an excellent window for hiking and canyon day trips before winter. A strong second choice to spring.
Winter (December-February): Mild by most standards (10-18°C daytime) but noticeably cooler at night, occasionally near freezing. New Year's Eve on the Strip is one of the busiest, most expensive nights of the year; outside of that, winter offers the lowest hotel rates and thinnest crowds.