Larry Bartels says the current "drought may not be entirely irrelevant for the upcoming presidential election":
Several years ago, Christopher Achen and I examined the impact of droughts and floods in presidential elections throughout the 20th century. We found a surprisingly strong and clear tendency for voters to punish the president’s party when their states were too wet or too dry. In the 2000 election (the most recent in our data), we estimated that Al Gore got about 2.8 million fewer votes than he would have under ideal climatic conditions.
Count me unconvinced.