The United Kingdom is heading for its third general election since 2015. Given that the executive and parliament are in a state of deadlock, this is no great surprise, but the exact timing has caused comment. Voting will take place on 12 December, and it may be difficult to obtain a high turnout during the festive season. There might also be other knock-on effects. “December election could bring down curtain on nativity plays,” warned The Times when the date was under discussion, as schools and church halls may be needed as polling stations.

Historically, though, winter elections, which we define here as those held between November and February, are not particularly unusual, even if every election over the last four decades has been held in April, May or June. In 1906, for example, in a pre-1918 era when polling was stretched out over days or weeks, voting began on 12 January and concluded on 8 February.

In the 19th century, winter elections were quite common, although the most popular month was August. After the Third Reform Act of 1884 extended the franchise dramatically, elections in that month tended to benefit the Conservatives, as many working-class town-dwellers were in the countryside helping with the harvest and thus unable to vote.

By contrast, of the 31 elections that have taken place since 1900, none has taken place in either August or September, although there is no rule that prevents it. During the 20th and 21st centuries, May and October have been the most popular months, scoring six elections each. June is a close second with five, but there have been four polls in February, and November and December have had two each.

Sometimes, politicians chose to go to the polls in the winter because they believed the national needs required it

So what factors determine when elections take place? Prior to the 2011 Fixed-term Parliaments Act (FTPA) the decision to call an election rested mainly with the prime minister, exercising a so-called ‘prerogative’ power on behalf of the crown. Where possible, of course, he or she would weigh the date carefully, taking particular account of the likely state of the economy at the point that voters would make up their minds.

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But where events turned against leaders, they did not always have that luxury. At the end of 1905, Arthur Balfour resigned as prime minister, calculating that the opposition would not be able to form a government, and that he would return to office, triumphant and strengthened. But the Liberals confounded him, and Sir Henry Campbell-Bannerman, the new prime minister, quickly called an election for the new year. Balfour’s Conservatives were soundly defeated. Two further winter elections took place respectively at the start and finish of 1910. The Liberals, led by HH Asquith from 1908, were locked in a battle with the Conservative-dominated House of Lords, and it was the workings-out of that crisis that determined the need for chilly season voting.

Seeking a mandate for change

Sometimes prime ministers chose to go to the polls before they were obliged to do so because they believed that national needs required it. In 1923, Stanley Baldwin called a snap election for December because he was convinced that unemployment could only be cured by a system of protective tariffs, and that he required a new mandate from the people in order to introduce such a system. He lost his majority. Another Conservative premier, Ted Heath, wanted the electorate to give him fresh authority in his government’s battle with the miners. He too went to the country early, in February 1974. The outcome turned out to be as unpredictable as the British climate: widely considered the favourite, Heath was narrowly defeated by Labour’s Harold Wilson.

Wilson’s successor, Jim Callaghan, declined to call a potentially advantageous election in the autumn of 1978, and struggled on through the industrial unrest that became known as the winter of discontent. In the spring of 1979, his government was narrowly defeated in a vote of confidence in the House of Commons, triggering an election that took place in May.

Subsequent governments established a pattern of early summer polling, and this became formalised by the FTPA. However, as we have seen in 2017 and 2019, the requirement can be overthrown if circumstances seem to demand it and if the necessary number of MPs agree.

When winter elections were regarded as politically necessary they were not especially controversial, however hard-fought the issues might be. Yet they sometimes provoked a degree of concern, as when, during the first of two general elections in 1910, The Lancet published an editorial on “The Medical Aspect of a Winter Election”.

The article expressed anxiety not for the voters but rather for the candidates and their active supporters, who were all said to lead “a life of dangerous stress” during elections. “To the mental and laryngeal strain which they have to undergo must be added the unaccustomed exposure to which they are submitted, particularly in rural constituencies.” Moreover: “Long evenings spent in chilly motor-car rides from place to place are interspersed with speech-making in the stuffy atmosphere of village schools, a constant alteration between the extremes of heat and cold which cannot fail to try the strongest.”

Because of geography and divergent weather conditions, such difficulties were not felt equally across the country. In 1931, when the election took place at the end of October, the Dundee Courier judged that the Western Isles constituency was “probably the world's worst for a winter election”. If the winter gales were blowing, “then the candidate is pretty well anchored, for all round the coast there is little protection, and there are swift-running tides that even without a gale give anxious moments to a landlubber”. This would give the advantage to an incumbent MP, as a less-well-known challenger would have little opportunity to meet the voters in person.

Today, technology can mitigate some of the more serious problems posed by a winter election – but, between them, meteorology and psephology offer no exact predictions as to the result. Although folk wisdom suggests that good weather generates high turnout and therefore benefits Labour, the case is, at best, unproven. “The sun is out, and so are the Tories,” said a buoyant Neil Kinnock on election day in April 1992, but on the night it was John Major who was returned to Downing Street. This year, it remains to be seen who the weather will deliver an early Christmas present to.

Richard Toye is head of history at the University of Exeter. His books include The Roar of the Lion: The Untold Story of Churchill's World War II Speeches (OUP, 2013)

This article was first published in the Christmas 2019 issue of BBC History Magazine