The current presidential race between Kamala Harris and Donald Trump is shaping up to be an extremely tight contest. Any number of last-minute factors might earn votes for one candidate or the other. Late-breaking economic news, international conflicts, personal gaffes or revelations – all may be enough to tilt the election.

There are also factors that have absolutely nothing to do with the candidates themselves or national and international conditions, but can affect a close election. These are what you might call the random factors.

The most prominent of these wild cards is the weather on Election Day. As I say in my recent book, “The Random Factor,” the weather is notoriously difficult to predict because of its random nature. Yet it can have a decisive influence on who wins and loses in a close election.

Research has shown that bad weather such as rain or snow tends to suppress voter turnout. For less motivated voters, harsh weather may be enough to keep them away from the polls on Election Day.

In general, studies show that this tends to favor the Republican candidate. One reason is that analyses have indicated that among Democrats, there is a slightly higher percentage of less-committed voters compared with Republicans.

As a result, when the weather turns bad, somewhat fewer Democratic voters show up to vote for their candidate, resulting in a slightly greater percentage of voters casting their ballots for the Republican candidate.

There have been two elections in modern times where the weather exerted a direct effect upon the outcome. The first was the extremely close 1960 election between John F. Kennedy and Richard Nixon, in which 118,000 popular votes separated the two. Had the weather been much more rainy and snowy on Election Day, researchers have found that Nixon would have won the states of Delaware, Illinois, Minnesota, Missouri, New Jersey, New Mexico and Pennsylvania, and therefore the presidency, by a comfortable margin.

The other presidential contest influenced by the weather was the 2000 race between George W. Bush and Al Gore. The election came down to Florida, which Bush won by 537 votes. Much has been made of the controversies surrounding the butterfly ballot, hanging chads, suspension of vote counting and so on. But had the weather in several Florida counties been drier on that day, Gore likely would have won the state and become the 43rd president of the United States.

Could the weather on Nov. 5, 2024, influence the election results? The answer is most certainly yes.

The contest between Harris and Trump may very well come down to the states of Wisconsin, Michigan and Pennsylvania. All three of these states are subject to extremely variable weather conditions in early November. It may be that Harris wins the election as result of favorable weather in one of more of these states, or that Trump wins because of bad weather in certain key counties.

The fact that bad weather has traditionally helped Republican candidates may be one of the reasons why the Republican Party and Trump have been much more resistant to allowing either early or absentee voting. This style of voting removes the weather effect and thereby neutralizes a Republican advantage that can occur on Election Day.

Although the weather is the most well known of the random factors that can influence an election, there is one more interesting element that could affect the outcome. Researchers have found that if the hometown sports team is doing well, particularly with a win in the 10 days before election by the college football team, voters are slightly more likely to vote for the incumbent in a presidential race.

As scholars Andrew Healy, Neil Malhotra and Cecilia Hyunjung Mo write, “We find clear evidence that the successes and failures of the local college football team before Election Day significantly influence the electoral prospects of the incumbent party, suggesting that voters reward and punish incumbents for change in their well-being unrelated to government performance.”

In describing what the scholars call “the subtle power of irrelevant events in shaping important real-world decisions,” they explain that the reason for this effect is that when your team is doing well, you may also experience a psychological boost. And voters who are feeling good about themselves and their immediate conditions are more likely to vote for the incumbent rather than for the challenger.

Although Harris is not an incumbent, she is the sitting vice president and therefore may benefit from such an effect.

The moral of this story is that the Trump campaign should be praying for bad weather along with hoping the Big Ten football teams in Wisconsin, Michigan and Pennsylvania suffer devastating loses on Saturday, Nov. 2, while the Harris campaign should be rooting for clear skies and triumphant Big Ten victories come Election Day.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Mark Robert Rank, Arts & Sciences at Washington University in St. Louis

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Mark Robert Rank does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.