Las Vegas
Las Vegas is hopping between Memorial Day and Labor Day, when visitors crowd around the pools and in air-conditioned casinos during the day in order to beat the 100-degree-plus temps outside. The months bookending summer are also warm but a bit more forgiving; March and October are particularly pleasant. December and January are the slowest tourism months of the year, but the city dresses up in holiday fashion, so those who visit are in for a festive experience.