Could rainfall have swung the result of the Brexit referendum?

Previous studies have shown that weather conditions may affect voter turnout, sometimes in ways that could plausibly swing the result of a close election. On the day of Britain's EU Referendum, the presence of torrential rain in the South-East of England and Northern Ireland raised concern in the media that voter turnout could be affected in a manner that favoured the Vote Leave campaign. To test this assertion, this paper takes data at the polling district level and overlays interpolated rainfall data using geographic information system (GIS) technology. Despite widespread expectations to the contrary, our analysis shows that the rain had the greatest effect on the leave vote, reducing the Brexiteer tally by as many as 4618 votes in one district. We find that if the referendum had taken place on a sunny day, there would have been a small increase in the margin of victory for Vote Leave.