The skies opened up over Waikato yesterday but the great downpour failed to deter those who flocked to the region's holiday hot spots for the "first taste of summer".

Metservice meteorologist Nic Bonnette said a severe weather watch was issued for Waikato and, as at 7pm last night, there had been more than 20 millimetres of rain.

There had been 21mm of rain at Hamilton and 14.2mm recorded at Paeroa.

However, that was expected to ease back overnight and isolated showers were forecast for today.

Raglan Kopua Holiday Park manager Mary Clark said Labour Weekend was often the "first taste of summer" and yesterday's weather had been "pretty sad for everybody".

"Not much of summer this weekend," she said.

"It's just so wet and so horrible, such a contrast to [Saturday]."

However, despite the deluge, most people had decided to brave the weather.

"Hopefully they've got a good book and the kids have got PlayStations or jigsaws or something to keep themselves occupied.

"It's pretty nasty out there, so I think they'll just hole-up for the day and toodle off [on Monday]."

Mrs Clark said she hoped the weather would blow itself out and make way for a "blinder" summer.

"We can't have two horrible summers like we had last year."

Whitianga's Mercury Bay Holiday Park operator Helena Stratford said accommodation was fully booked over the weekend, with the Whitianga Bath Tub Race and Birdman Competition bringing people into town.

Other than a few squally showers, the worst of the weather hadn't reached the bay by yesterday evening, she said.

"It's not been too bad over this side. People came prepared with their gumboots and their rain jackets and they've been in town enjoying the township."

Bath Tub Race and Birdman Competition organiser Kevin Shaw said up to 1000 people came out in the wet to support the event at Whitianga Waterways yesterday.

"It was pretty rainy and windy, but the public got in behind it and we had a pretty good crowd there. Everybody was soaked through, but at the end of the day everyone got into the spirit of it."

It was the third year for the Bath Tub Race, in which 25 competitors built boats using a bath and raced at speeds over 40kmh.

Mr Shaw said it was the first year for the Birdman Competition, which attracted only four competitors, who launched themselves off a jetty, wearing various flying apparatus. None achieved full independent flight.

The event raised about $2000 for Hot Water Beach Lifeguard Service and the Whitianga Coastguard.

- © Fairfax NZ News