Here are a few notes and references which may help you.
Statistically, the high temperature for April 1 has been 74.3 average and the low has been 52.8. Those are the averages and the highs could be in the 80s and the lows could be in the 40s. Over the years we've mostly had good weather but we've seen a few very hot days and a few cold and windy evenings. One year I remember that we got complaints about it being cold and windy on the golf course.
One thing to keep in mind is that most (not all) of what you'll do will be inside, in 68-75-ish temperatures.
I'm going to suggest reading a few articles. These are somewhat dated and could use a good work-over but they are still relevant. The first is on dressing and the weather:
http://www.geekbabe.com/dlv/mydlv/blogs ... e-weather/This was written when our event was usually held in the middle of April, so mentally subtract a few degrees as you read along.
Another is the visual dress notes page:
http://www.geekbabe.com/dlv/mydlv/blogs ... ess-notes/It's about a decade old but still relevant and covers casual, golf, sightseeing, dressy, and even touches on the exotic.
The best examples of dress for our event can be found on the various follow-up pages for recent years. I would suggest starting here:
http://divalas.vegas/dlv2015n/The pages for Activities, On the Town, People, and Dining will give you many many examples of dress for our various activities.
Hope this helps.