Weather: Cantabrians preparing for deluge as red alert-level rain starts falling

Cantabrians have spent Saturday madly preparing for a deluge.

A huge amount of rain is forecast to be dumped - some areas are expecting to receive up to three months worth in three days.

That would make it the most significant rainfall in a decade and weather forecasters are urging people to take it seriously.

MetService has issued a rare red alert warning for the area south of Amberley to the Waitaki River where farmers have already swung into action to protect their livestock.

North Canterbury farmer Cameron Henderson has been feeding his livestock before the heavens well and truly open.

"200mm of rain for us is really extreme, I've never seen that here before," he says.

MetService is warning Cantabrians to prepare for steady, heavy rain that could cause widespread flooding.

Up to 300 millimetres of rain is forecast, prompting a red warning - reserved for only the most extreme weather events.

It means people need to take immediate action to keep themselves safe, which could be as simple as clearing leaves from drains.

"You get the surface flooding pretty quick, hoping it won't be too bad. Seen people out getting prepped for it," New Brighton resident Mike Jarrett says.

Business owners in Sumner are all too used to flooding. Some are resorting to sandbags.

"We're hoping it will work, if not then we might do a bit more next time," says Fire and Slice woodfired pizzeria owner Bal Singh.

Next door business owner Adrien Taylor was improvising -  doing what he could with what he had.

"Chopping up a yoga mat and trying to use the rubber to seal the door off and hopefully stop the water from getting in," he says.

But it's those areas you can't waterproof that could feel the biggest impact.

"The rain that we're going to get is more than we've had in the last eight months on this farm," Henderson says.

"I would've preferred that to have been a bit more even over that time but Canty has a habit of catching up at some point."

Just a bit more than Cantabrians bargained for.