Aucklanders could face a nightmare commute home this evening if Team New Zealand claims victory in today's sailing of the America's Cup.

People are being told to expect their travel out of the city both in private vehicles and public transport to take a lot longer with big influx of spectators and city workers heading to the waterfront to take in today's racing action.

Transport authorities are even warning that inner city roads could close at short notice and rush hour could last for hours.

Hundreds of pleasure craft are once more expected to head out on the Waitemata Harbour today to watch Team New Zealand vie for race seven line honours against a trailing Luna Rossa.

With the cup glory on the horizon, organisers are expecting an equally bumper crowd at the Viaduct after 30,000 people turned out yesterday in the hope of a cup result.

Auckland Transport said the combination of cup racing combined with St Patrick's Day celebrations could mean downtown roads closed at short notice if crowds built up suddenly.

"As the potential of a winning match nears, we are expecting large numbers of spectators and city workers to head towards the action and big screens in the race village. We also expect people to then stay longer in the city and in the race village for the return of the sailing teams, prize-giving and socialising at the bars and restaurants.

"Combining racing fans and people enjoying St Patrick's Day, the roads and public transport will be busy, extending the city's evening peak time travel congestion. Give yourself a bit more time to get home or enjoy the festivities."

Ahead of today's racing on Course A those monitoring the spectator flotilla were also expecting an equally busy day on the water.

"With the excitement of the race yesterday with the lead changes and how close it was and it really is do or die now for the Italians I think we will see quite a few craft out there," said Coastguard's John Cowan.

"Also we're using Course A which is off the East Coast Bays so viewing from North head, Tamaki Dr, Bastion Point is not going to be possible so the only way to see it up reasonably close is on the water or in front of the TV."

Cowan said around 760 vessels took to the water yesterday to watch racing.

Unlike yesterday there would be no restrictions around the harbour save the 5 knot speed restriction for those travelling on the way home from the racecourse.

The fan flotilla is expected to turn into a supporting parade should Team New Zealand win a race and claim the cup.

Around 90 minutes after the end of the race an awards ceremony is expected to take place on the America's Cup Village main stage where the Auld Mug will be taken from its secure holding place at the Royal New Zealand Yacht Squadron and presented to the triumphant crew.

That ceremony is expected to take up to nearly an hour.

It will be followed by a press conference.

At 8pm to mark the final night of racing there will be a special thank you from the host city to Aucklanders to acknowledge their support of the event and congratulate the winning team.

The Harbour Bridge, Skytower and Auckland Museum will all be lit up in the winning team's colours.

Between 9pm and 9.30pm fireworks would light up the sky over Waitemata Harbour.

Armitage said there was a real buzz in the village and hospitality businesses were doing a roaring trade.

"We had around 30,000 people in the village yesterday. If we have an outcome we'll have people flocking down there to take the action in. Looking forward to another busy day."

And should racing finish today he couldn't have imagined a more perfect ending.

"It's a very happy coincidence that it's happening on St Patrick's Day. When it dawned on me earlier in the week I thought that would be a fitting way to go out. Obviously St Patrick's Day is a pretty big event in its own right but to combine that with the possibility of concluding the America's Cup I couldn't think of a better way for us to have the city celebrate what we've just had to experience."