People wait at Waterloo Station PA Wire / Press Association Images PA Wire / Press Association Images / Press Association Images

TURNOUT IS SET to be a crucial factor in the Brexit referendum, but heavy rain and thunderstorms have been causing slow journeys this evening for thousands of London commuters.

Voters have been taking to Twitter to say they fear they won’t make it to polling stations before they close:

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Southeast England was hit by up to 1.75 inches of rain overnight — roughly the average for all of June — and another band of thundery rain swept through this afternoon.

Doug Wilson, a flood risk manager at the Environment Agency, told AP that “torrential downpours across the South East, including London, could lead to further surface water flooding and significant disruption to travel.”

A handful of polling stations in London opened late or had to relocate because of flooding, while signal failures caused by flooding shut down sections of the London Underground subway system and several train lines into the capital.

The Rail Delivery Group said train services would be severely disrupted this evening and people should head home early if they can.

Thousands of people crammed into Waterloo and other London train stations, eyeing signboards full of cancelled and delayed trains.

The disruption could hit the turnout for Britain’s referendum on whether to stay in the 28-nation EU, since many people go to polling booths after work.

The polls are due to close at 10pm. Follow our liveblog throughout the night here.

- Additional reporting Aoife Barry

Read: LIVEBLOG: The United Kingdom votes on whether or not to leave the EU>