October average high is 82° F (28° C)and average low is 54° F (12° C)
I suggest You bring a light jacket or sweater if You visit Las Vegas in October. You probably will not need it and You will probably have some hot days but averages are just averages and better to have the jacket than have to buy it. It really is smart to have a light jacket or sweater all the time in Las Vegas because the Casinos can really get cold at times. Casinos have to cool down a very large space and sometimes they go a little to far, maybe expecting more body heat. What You are left with is a very chilly Casino.
October is the best time to go to Las Vegas, the weather is just one of the reasons why. The good news is Las Vegas is fantastic in October. The bad news is Las Vegas is fantastic in October so the hotel rates are about as high as they get other than New Years and in March during March Madness.
The reason the hotel rates are high in October is because the weather is perfect and its FOOTBALL season. Expect the sports books to be full and loud.
Higher rates would be a problem in most any other city, but in Las Vegas, saying rates are higher means the rates are still a lot better than 99 percent of anywhere else but just higher than usual.