Polls open in US midterm elections: When voting starts and ends state by state

Voting has begun in the United States midterm elections on Tuesday, with more than 230 million eligible voters able to head to the polls to decide who will represent them in Congress.

All 435 House of Representatives seats and 35 of the Senate's 100 seats are being contested. Voters in 36 states will also elect governors. Republicans currently hold both chambers.

Voting hours are determined and set by each state, so opening and closing times differ across the country.

The first polls opened in Vermont at 5am local time. Voting in New Jersey, Virginia, Connecticut and Kentucky started at 6am.

Voting in Georgia, Florida, Pennsylvania and New York started between 6am and 7am, while Ohio and North Carolina saw voting start at 6:30am. In Michigan, polls opened at 7am.

Polls close in waves across the country, with the earliest closures at 6pm in Indiana and Kentucky. Voting in Michigan closes at 8pm and in Kansas at 7pm local time, while polls in Iowa close at 8pm.

Alaska is the last to close, at around 1am Eastern Time on Wednesday.

The first results could start arriving on Tuesday as polls begin to close. Results will continue to come in throughout Tuesday evening and on Wednesday as more states finish voting and officials release their counts.

However, the first reported results will not necessarily mean a winner has been announced. Election officials release vote counts as ballots are processed, while news organisations such as the Associated Press analyse the results and determine when a race can be called.

Closely contested races could take hours, or even days, to call. It might not be immediately clear which party will control Congress.

Voters can cast ballots by mail, early or in person on election day. Many mail, provisional and other ballots are counted after election night, which is why tallies can take a few days, or even weeks, to finalise.

Senate Democrats need a net gain of four seats to reach a majority. House Democrats need three seats for a majority.