With basically a billion reports of long lines at polling places today, many of them outside, it's natural to wonder how weather affects voter turnout. Would you like to stand in the rain two hours to vote for Mitt Romney? No, you would probably not.
[E]ach inch of rain experienced on election day drove down voter turnout by an average of just under 1%, while each inch of snow knocked 0.5% off turnout. Though the effect of snow is less on a “per inch” basis, since multiple-inch snowfall totals are far more common than multiple-inch rainfall events, we can conclude that snow is likely to have a bigger negative impact on voter turnout.
Furthermore, Gomez et al. noted that when bad weather did suppress voter turnout, it tended to do so in favor of the republican candidate, to the tune of around 2.5% for each inch of rainfall above normal. In fact, when they simulated the 14 presidential elections between 1948 and 2000 with sunny conditions nationwide, they found two instances in which bad weather likely changed the electoral college outcome – once in North Carolina in 1992, and once in Florida in 2000. The latter change is particularly notable, as it would have resulted in Al Gore rather than George Bush winning the presidential election that year.