I've lived in Las Vegas for about 7 years. Today there happens to be some thunder and a bit of rain. It disappoints the visitors, but we like when it rains at all. When you only get 4 to 10 inches in a year, with well over 300 sunny days, some clouds and rain are nice to see. No matter when you come, rain is unusual. Snow is very rare as maybe a half inch on a day every few years. A cool day in summer is when the high stays under 100F. A cold night in winter is when 30's are found.
December 2012 = Daytime highs 53-72F, Late night lows 30-47F, 0.49" rain total over 2 days.
December 2013 = Daytime highs 45-69F, Late night lows 26-40F, 0.05" rain total over 2 days.
December 2014 = Daytime highs 53-75F, Late night lows 30-43F, 0.30" rain total over 6 days NYE trace Snow
December 2015 = Daytime highs 46-70F, Late night lows 29-46F, 0.01" rain total over 2 days.
December 2016 = Daytime highs 48-70F, Late night lows 30-47F, 0.05" rain total over 5 days.
January 2013 = Daytime highs 50-65F, Late night lows 23-38F, 0.43" rain total over 3 days.
January 2014 = Daytime highs 49-73F, Late night lows 34-57F, 0.00" rain total
January 2015 = Daytime highs 54-73F, Late night lows 29-46F, 0.87" rain total over 6 days.
January 2016 = Daytime highs 48-74F, Late night lows 27-49F, 0.46" rain total over 4 days.
January 2017 = Daytime highs 54-66F, Late night lows 33-46F, 0.90" rain total over 7 days.
Daytime high over the 10 months covering 5 years went as low as 46 and as high as 75.
Days reaching the 50's or 60's are fairly normal as a high temperature. A jacket or a sweater are considered normal during the day.
The low reached down to 23F and a particularly warm night at 57F. Reaching down into the high 30's or low 40's is fairly normal. Rarely does the word "freezing" apply but how about chilly nights if outside late.
Putting it together, about 12% of days see some precipitation or typically once a week, and its a few tenths of an inch on a day with rain. Snow is unusual in any particular winter.
If you are driving in from Southern California you say Las Vegas is cold.
If flying in from Chicago you would say its fairly comfortable, but a bit chilly at times.
There are few places with indoor pools, but an outdoor lunch al fresco is appropriate on some days.
It's cool enough for people in their 20's and 30's to be out and about comfortably and walking is more common than in the summer heat.
You can be sure the winters are very different from the summers. October, November, March, April, and well into May are considered the nice weather months. But the pool parties of the summer, and brisk weather in the winter are also good for people looking for it. For visitor counts, though conventions versus tourists vary, 3.3 million to 3.8 million per month is the range. Every month is considered a nice time for a visit. Holidays and big conventions get crowded, and often most weekdays are a bargain.
Per comment: Wednesday Dec 17,2008 3.5 to 8 inches through the valley and schools closed.
Melted within a couple of days.
9.9 inches on one day in January 1979.
2 inches on Dec. 15, 1967; 0.4 inches on Dec. 5, 1972; 1 inch on Dec. 6, 1998; and 1.3 inches on Dec. 30, 2003.
6 days with measurable snow since 1967 (50 years)