More than 30 hours of wet weather is on the way for parts of the South Island, with heavy rain warnings for northern and western areas and the risk of severe gales later as two weather systems make their presence felt, MetService says. 

The warnings came as a front moved northwards over the South Island yesterday and was set to continue today, bringing with it heavy rain, the national weather service wrote on its website. 

The first of two weather systems hit the country yesterday. 

“The ranges of the top and western South Island are expected to see the bulk of the rain … for the top of the South Island, it’s a long period of wet weather expected from [today] to [tomorrow] with only a brief lull between the two systems.” 

Streams and rivers could rise, with surface flooding and slips possible, and thunderstorms were possible for the West Coast and Canterbury high country near the Southern Alps, MetService wrote. 

Meanwhile, the second weather system is expected tomorrow, bringing further heavy rain, strong winds and large wave conditions. 

“Further warnings and watches are likely in the coming days.” 

Up to 350mm – and possibly 400mm about the ranges – was expected in Tasman District northwest of Motueka from noon today to 7pm tomorrow. 

“Peak rates of 25 to 30mm an hour expected during [tomorrow] with thunderstorms possible,” MetService wrote on its severe weather warnings page. 

Up to 300mm of rain is also expected around the ranges of the Buller District, with lesser amounts near the coast over 33 hours from 10am today. 

MetService's 3-day rain radar showing the expected situation over the South Island at 3pm on Thursday. Heavy rain warnings have been issued for parts of the South Island for today and tomorrow. Image / MetService 

Rainfall rates could peak at 15 to 25mm/h tomorrow, with thunderstorms possible, MetService wrote in its heavy rain warning for the district. 

A 23-hour heavy rain warning kicked in for Westland District at 8pm yesterday, with up to 300mm of rain expected about the ranges and smaller amounts on the coast, MetService wrote. 

“The largest accumulations are likely about and south of the glaciers, where some models indicate 350mm is possible about the ranges.” 

Peak rates up to 35mm/h were expected today, with thunderstorms possible, and another period of heavy rain expected from tomorrow afternoon. 

A heavy rain warning for Fiordland north of Doubtful Sound ends at 11am today, but more heavy rain is expected from tomorrow afternoon. 

The headwaters of Canterbury lakes and rivers south of Arthur’s Pass are also under a heavy rain warning until 6pm today, with the same warning for the headwaters of Otago lakes and rivers ending at 11am. 

Nelson Lakes National Park, the Richmond and Bryant Ranges and the Rai Valley are under a heavy rain watch from tonight until 9pm tomorrow night, with a high chance of upgrading to a warning, MetService wrote. 

A heavy rain watch for Grey District ends at 9pm tonight, with a moderate chance of being upgraded to a warning.