A long-standing thought is that the worse the weather, the better it is for Republicans and vice versa.
Some reports say there is no emperical evidence one way or the other.
However, one study in the Journal of Politics showed for every inch of rain, Republicans can expect an extra 2.5% of the vote. At the same time, during stormy weather, voter participation declines by 1% for every inch of rain.
The explanation is that a traditional group of the Democratic Party - low-income and elderly voters - find it difficult to travel to the polls in stormy weather.
One can imagine how even these small percentages could affect such tight races.
With that said, as a meteorologist (not a politician or pundit) I do not create the weather, and did not produce that survey - just reporting the numbers and not rooting for any party or candidate. In fact, simply google "weather - voter - turnout" and you can see numerous articles on the subject, since it certainly can be a hot topic on Election Day.