No, not because of the weather. It was a flashmob-type "stay still for five minutes" event, inspired by a similar event in NYC.
Much of this event was organized through Facebook. Several Yulbloggers participated, including the ever-thoughtful Fagstein.
The NYC version does look more impressive, obviously. I still wish I could have participated. Maybe we should do one in Austin during SXSW.
Here's a video of the NYC version: