Coming with these winter storms were some massive ocean swells.

A burst of heavy swell was pushing up the west coast from Fiordland to Northland through today.

Another pulse late Friday and into Saturday could see swells of 6m around Piha.

"It has a long period too, 16 seconds, so the waves will be quite powerful," Martens said.

Today's weather
• Whangārei

A few showers, more frequent from afternoon. Evening thunderstorms and hail possible. Westerlies. 17C high, 12C overnight.

• Auckland

A few showers, more frequent from afternoon. Evening thunderstorms and hail possible. Westerlies. 17C high, 12C overnight.

• Hamilton

A few showers, more frequent from afternoon. Evening thunderstorms and hail possible. Westerlies. 15C high, 9C overnight.

• Tauranga

Fine until afternoon, then a few showers. Westerlies picking up morning. 16C high, 10C overnight.

• New Plymouth

Showers becoming frequent this afternoon, possibly heavy and thundery. Westerlies. 16C high, 9C overnight.

• Napier

Fine, then cloud increasing and chance evening showers. Northwest becoming strong and gusty. 18C high, 10C overnight.

• Wellington

Fine, then showers developing afternoon. Thunderstorms possible tonight. Northwesterlies rising to gale. 15C high, 9C overnight.

• Nelson

Cloudy periods, then showers from midday. Westerlies. 14C high, 3C overnight.

• Christchurch

Fine with high cloud. Strengthening northwesterlies. 14C high, 0C overnight.

• Dunedin

Showers, less frequent from afternoon, then clearing evening. Strong gusty westerlies. 11C high, 3C overnight.