Rain or cool weather means lower Democratic turnout. Does this mean those without cars don’t show if the weather is not good.
"These findings significantly illuminate the theory in regards to voter turnout. In
particular, these results show that the primary exogenous mechanism through which
turnout affects elections is the composition effect. In other words, when turnout is
increased, newly mobilized voters are disproportionately Democratic. Furthermore, these results illuminate a question that has been claimed to be unanswerable: If one could increase voter turnout, would it help Democrats? We find that the answer to this question is, resoundingly, yes.”
"The Joke Isn’t on the Democrats? The Partisan Effects of Voter Turnout"
Alexander Kendall, Political Science, Stanford University