In a Q&A last week on twitter, Hamrick was asked how many walk-up tickets we sell on game day. He replied that it varied from game to game but they have sold as many as 3,500 on gameday.
While some of those walk-up sales have most definitely bought in advance this week I also feel like the buzz around this game may bring more people out on game day that don't usually attend games.
By the way, weather.com this morning has the forecast for Sunday as sunny, 93 degrees with only a 10% chance of a shower. Going to be hot and humid.