The wind is returning tomorrow for America's Cup racing but spectators can expect rain

NYYC American Magic fans make the most of the fine weather on the boat, Mercury Rising, during Prada Cup action on Saturday. Photo / Brett Phibbs

The winds will be back for tomorrow's third day of racing in the Prada Cup, but foul weather is forecast for spectators along the Auckland waterfront.

Today's sailing was marked by patchy winds with the yachts flying in the sub 10 knot conditions one minute and flat in the water the next. The second race between American Magic and Team UK was delayed to get more breeze in the sails.

"It should be pretty good for sailing tomorrow," said MetService forecaster Aidan Pyselman.

He said the winds in the morning will be light, but a northwesterly will develop later in the morning and reach 15 knots by lunchtime and be pretty good for racing in the afternoon.

Tomorrow's northwest winds of 10 to 25 knots will be similar in strength to yesterday's southwest winds that saw Team UK fly out of the blocks and bag back-to-back wins against American Magic and Luna Rossa.

Weatherwise, it won't be good tomorrow in the City of Sails with cloud in the morning and a front crossing the city late in the afternoon with showers and potential thunderstorms through into the evening.

For the rest of New Zealand, Pyselman said the weather is looking pretty unsettled with a deep low sliding in from the south of the country.

There is a severe heavy rain warning for the west of the South Island and Nelson could cop some heavy rains. Thunderstorms are forecast for the south and west of the South Island.

Pyselman said as the front moves north, cloud will increase followed by rain and showers with potential thunderstorms for the west and north of the North Island.

Everywhere is probably going to see rain during the day, said Pyselman, although eastern parts of the North Island - Wairarapa, Hawke's Bay and Gisborne - will have pretty good weather in the morning.