For our money, the best month of the year in Las Vegas is May.
March is a fickle month. Temperatures are noticeably warmer than the chilly days and cold nights of February, which has a mean temperature of 56 degrees, an average maximum of 69 degrees, and an average minimum of 42. In March it can rain on occasion and the winds, always a concern in Las Vegas, can be high. Many of the pools are still closed in March and you’re wise to bring a jacket for the inevitable cold snaps and cool evenings.
In April, the winds tend to subside and the weather is milder than March. The mean temperature in April is a comfortable 64 degrees, especially when the sun is shining; the average maximum is 78, which means temperatures can rise into the 80s, while the average minimum is 50. The winds subside and most of the pools are open. You should still bring a sweater or light jacket, just in case it gets cold in the evening.
May is just about perfect weather, with a mean temperature of 74 degrees, and average max of 88, and an average minimum of 60. This is Las Vegas at its best, the potentially cool days behind us and the sizzling heat of the summer still ahead. Hot weather can arrive with a vengeance at the end of the month, so mid-May, the second and third weeks, is best.
Summers in Las Vegas, as everyone knows, are hot Hot HOT! And dry. June’s average-max temperature is 99, July’s is 105, and August’s is 102. The sun makes it feel even hotter. As for clothing, the skimpier the better; best is to peel off your skin and sit in your bones. Cyclonic storm fronts in summer, which can drop an inch of rain an hour, are carried in by ferocious winds that have been known to shift all the sand from the west side of town to the east. And vice versa.
By September, the mean temperature is down to 80, though the average high is still up there at 95 degrees. But the evenings are balmy, with an average minimum of 65, the pools are open, and there’s little to no chance you’ll need a sweater or jacket -- except maybe in the casinos, which get colder as the ambient temperatures get hotter.
In our opinion, the last week in September and the first week in October are a close second to mid-May for the best time to visit, weather-wise.
