More rain is on the way for Auckland this week – but a meteorologist says it will take a solid month of wet weather to alleviate the worst drought in quarter of a century.

Niwa's Ben Noll said the 270mm rain shortfall that Auckland faced at the start of the week had dropped slightly to 250mm, thanks to a bout of light rain.

"But it's important to remember that when we see it raining in Auckland, that doesn't mean that the drought is over by any stretch on the imagination."

Noll said a 250mm shortfall was "still pretty extreme" – and symptomatic of an extraordinary dry period that has plunged Auckland's dam levels to 43 per cent capacity, compared with a normal average of 76 per cent for this time of year.

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The Lower Huia Reservoir in the Waitakere Ranges, pictured on May 22. About 34mm of rain has fallen there over the past week. Photo / Brett Phibbs
The Lower Huia Reservoir in the Waitakere Ranges, pictured on May 22. About 34mm of rain has fallen there over the past week. Photo / Brett Phibbs

The Hunua Ranges got about 3mm of rain yesterday and 30mm over the past week. About 14mm fell on the Waitakere Ranges yesterday and 34mm over the week.

Watercare was expecting 40mm to 60mm of rain this week, but slightly less than normal next week.

Yesterday, Aucklanders used 426 million litres of water – slightly more than a target of 420 million litres Watercare set for May, as strict rules around personal consumption remain in place.

Today, Hamilton Mayor Paula Southgate said her city looked likely to help Auckland with its looming water crisis - but any help would come with conditions to protect the river and Hamilton's long-term interests.

MetService meteorologist Peter Little said Auckland received welcome moisture yesterday and more showers are to come this afternoon - but less than 1mm was expected tomorrow.

"There could be another 5mm on Friday, possibly more on Saturday, and then more showers on Sunday and Monday – but with amounts not as impressive as we've seen today," he said.

"The good news is that we are maintaining a northeasterly flow, which is bringing showery weather and persistent rain for several days."

Noll however pointed out that this kind of weather was needed for much longer than a few days.

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"The rain we've seen in Auckland in the past couple of days - we're going to need it to do that for a solid month straight or longer, to get back to where we should be for this time of year."

After months of dry weather, soils were parched, cracked and hard, meaning they couldn't absorb moisture as easily as when they were plush.

"When you get a lot of rain falling on hardened ground, you get run-off.

"So, despite the gloomy skies, it is very important do not let your guard down at any rate - and certainly Watercare's dam storage levels would attest to that."

More rain was possible mid to late next week, but models also suggested a large ridge of high pressure could slide over the country in mid-June.

"That could spell another extended dry spell and we have been talking about that possibly becoming a theme once again, which is the last thing we need right now," he said.

"We need 250mm plus – and that's not coming any time soon. While just 25 days of 10mm rain would get you there, these are still few and far between."