Typically I wear long pants & a short-sleeved shirt during the day, but I make sure to bring a light jacket or light pullover or something for if it's really cold in the convention center.
At the end of each day (5PM or so when all the presentations are over) I go back to the hotel to change into shorts and some other short-sleeved thing for dinner / after-dinner activities.
If you try to wear shorts and/or too light a shirt during the day in the convention center, you might be cold.
If you try to wear long pants when you go outside in the afternoon/evening, you will burst into flames and die in agony .