Polls Open in Britain’s Historic EU Referendum (Photos)

Advocate to exit Europe Boris Johnson poses for a selfie photo with voters during a whistle stop tour of the country on the final day of campaigning before Thursday's EU referendum vote, in Selby, north England, Wednesday June 22, 2016. Photo: Andrew Parsons / Associated Press

LONDON — Polls opened in Britain Thursday for a referendum on whether the country should quit the European Union bloc of which it has been a member for 43 years.

More than 46 million people are

registered for the vote, which asks: “Should the United Kingdom remain a member of the European Union or leave the European Union?”

Polls are open until 10pm, with results due early Friday.

The referendum has exposed deep divisions over issues including sovereignty and national identity.

“Leave” campaigners claim that only a British exit can restore power to Parliament and control immigration. The “remain” campaign led by Prime Minister David Cameron argues that Britain is safer and richer inside the 28-nation EU.

Financial markets have been volatile ahead of the vote, with opinion polls suggesting a tight race.

Turnout is considered critical in the vote, as polling suggested there were a number of undecided voters. Those who waver at the end tend to go for the status quo, which would favor the “remain” campaign.

It was raining heavily in some parts of the country, which could have an effect on turnout. Downpours and flooding swamped parts of London and southeastern Britain. London’s Fire Brigade received hundreds of calls of weather-related incidents early Thursday, including some reports of flooding and lighting strikes.

The Environment Agency has issued four flood warnings and 22 flood alerts across the southeastern part of the country.

Sunny weather is predicted for much of the rest of the country.

Story: Danica Kirka and Jill Lawless