Las Vegas is a south-westerly city and has a subtropical hot desert climate. Therefore, it has very consistent weather: it is hot, dry and sunny. The city is surrounded by mountains and sits upon the basin of the Mojave Desert so there is very little humidity. It rains very rarely.
The average summer temperature is 33 °C whilst the average winter temperature is 8 °C.
Visit in any season as there are little more than temperature fluctuations to prepare for.
Dress and plan accordingly.