Nate Silver examined the turnout at various Occupy Wall Street rallies during this past Saturday. He notes a couple of reasons why more people might turn out in one city than in another, including racial politics, organizational technology, and city political structures. Here's another idea: temperature. Does cold weather keep people indoors?
To answer this question, I used Silver's rally turnout estimates (Excel file) for the 36 largest rallies and divided them by each city's 2010 population to get a per capita estimate. Then I collected high temperature data for each city on that date. Here's the result:
Also, there's a big heteroskedasticity problem in the data, and there just aren't many cases above 85 degrees. But dammit, I collected that data, and I was going to put the scatterplot up no matter what it said.