The wettest year Christchurch has experienced for several decades is headed for a swing in the other direction.

Consistent rain has led to the cancellation of sporting events, flooded parks and reserves, and foiled lambing season.

By the end of September, Christchurch had already exceeded its average annual rainfall total. It has showed no signs of stopping: the weekend's downpour amounted to two-thirds of the average October rainfall, just one week into the month.

The last time this much rain had fallen in the first nine months of the year was 1975, according to data from the Christchurch Airport weather station.

READ MORE: July flood closes roads, causes chaos in Canterbury

But this is likely to change in the coming months, with drier, warmer conditions than usual expected.

JOSEPH JOHNSON/STUFF A storm in July contributed to high rainfall totals in Christchurch.

The unusually high rainfall has been in large part due to three storms: two in April and one in July.

Rainfall in April was triple the average and 10 times the amount that fell in the same month last year, due primarily to two storms in quick succession.

Another storm in July caused widespread flooding and resulted in the Heathcote River bursting its banks. Together, April and July accounted for more than half of the city's usual annual rainfall.

Although the storms were the major cause of high rainfall, it has been more consistently rainy, too.

There have been 78 wet days so far this year, meaning it has rained the equivalent of two days per week –the highest number of wet days at this point in the year since 1974.

A day with more than 1 millimetre of rain is considered a wet day.

DAVID WALKER/STUFF Heavy rain over Easter weekend was the first of two major storms in Christchurch this year.

Because Christchurch is shielded by the Southern Aps, it is protected from the prevailing westerly winds, which make it the driest major city.

But several events this year had been caused by warm air arriving from the east, leaving it exposed, NIWA principal forecaster Chris Brandolino said.

"If the air comes from a place where it's rich in moisture, such as the tropics or the sub-tropics, and is brought down into eastern Canterbury, that's going to be fuel for rainfall," he said.

STUFF Rain totals in Christchurch for every day this year. The three spikes correspond to two storms in April and one in July.

"If you have the fuel, you need something to light it – that's low pressure, which lifts the air. If the air has a lot of moisture, it's going to rain out pretty hard.

"We've had a couple of events like that this year."

But temperatures over the rest of the year are likely to be above average for most of the country, Brandolino said.

Rainfall in coastal Canterbury is expected to be either below average or near average, meaning the run of unusually wet weather was likely over.

"It's pretty unlikely. I wouldn't say there's zero chance, but if you're a betting person you wouldn't put your money on that."

It is good news for the region's rivers, which have dried up over recent years, primarily due to low groundwater levels.

Around 87 per cent of monitored wells in Canterbury have above average water levels.

"The rain has recharged the groundwater levels," said Environment Canterbury groundwater science manager Carl Hanson.

"The water table across the region is now generally at above-average levels … It is likely that groundwater-fed streams, such as the lower Selwyn River at Coes Ford, will keep flowing over summer."

The rain has been a mixed blessing for farmers, however, some of whom have emerged from a years-long drought.

"We've had enough of the rain, but it's just mother nature," said North Canterbury dairy farmer Theo Sneek.

"For some farmers it's good, but not for us."

Sheep and beef farmer Jeanette Maxwell from Mt Hutt said the rain had likely affected the lambing tally.

"We would love to start tailing, but we haven't had a break in the weather," she said.

"We were moaning about a drought, but hey – not now."

Although it caused problems for some, the rain was a good sign for a region emerging from drought, said Federated Farmers South Canterbury provincial president Mark Adams.

"When I think about South Canterbury as a province, most people are grateful for this rain."