Weather: Severe thunderstorm watch for parts of drought-stricken upper North Island today

The first proper rain since the New Year has given drought-stricken farmers hope of a break in the extreme fine weather wreaking havoc on their land and animals.

But more is needed according to Federated Farmers Waikato president Andrew McGiven.

"At this stage we've probably only had about 5 millimetres. We're going to need more than this," McGiven said.

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The Te Aroha farmer said, however, that the first rainfall in more than six weeks was a hopeful sign.

"What it's going to do is probably give us hope that the weather pattern is broken and that those patterns of highs that have been sitting over us might have moved off and we might start getting some more rain."

McGiven said farmers needed at least another 20mm of rain over the coming days.

"If we get 25mm out of all of this over a day-and-a-half, it would be perfect. Just to wet the ground and make it less hydrophobic, so the water doesn't run off.

"When the ground gets so hard, when you get water on it, it just runs off the top - it doesn't soak in. It just makes the ground a little bit more receptive for that future rain."

He was pleased to hear about a severe thunderstorm watch put in place today by MetService.

"This rain, as small as it may be, is very welcome and hopefully it will hearten all us farmers that the pattern has changed and we might start getting some more fronts coming over."

Those on household tank water would also be relieved, after water supplies had run dry for many.

MetService meteorologist Andy Best said a front sitting to the west of the upper North Island would cross over Auckland between midday and 1pm.

"Already in western parts of Auckland we've seen places receive rain - Piha had 1.5mm of rain in the last hour [to 10.30am]."

Cape Reinga in Northland recorded 5mm of rain in one hour.

There had also been rain in the Waikato and quite of lot of it over Whanganui and northern Taranaki.

"We do have a severe thunderstorm watch in effect, associated with this front and that is from northeastern Taranaki, through Taumarunui, Taupō, Rotorua, Waitomo, Waikato and almost up to the Firth of Thames."

There was a possibility of thundery downpours Best said, and rainfall rates could exceed 5mm an hour in that region.

The forecast was valid up until 5pm today.

Tomorrow the situation would change. Today's front would clear the North Island tonight and would be followed by a couple of cold fronts, bringing relief to the humidity, mainly experienced in the upper North Island during past weeks.

Temperatures would remain in the mid-20s, according to a MetService graphic, because the cold front was relatively weak, Best said.

There could still be showers tomorrow, and rain may return at the end of next week.

Sunday's showers would come through into the Canterbury plains, North Otago, the West Coast, Marlborough and the Sounds, Southern Wairarapa and Wellington.

The rest of the country may see residual showers before it becomes fine again.