Further north, Auckland and Waikato will get passing cloud and fine spells before the front tracks north on Tuesday.
MetService meteorologist Devlin Lynden said the front would reach the lower South Island this morning, with strengthening northwesterlies announcing its arrival.
Up to 350mm could fall in isolated parts of the West Coast ranges, while strong winds would create another challenge for drivers.
For holidaymakers steering campervans or other high-sided vehicles home, Lynden said the gusts deserved particular attention.
“You will want to be thinking about those strong winds.”
Auckland will start on a gentler note, with passing cloud before northwesterlies gather strength in the afternoon.
Lynden said the strongest winds were likely to stay in the southern North Island today, although Auckland could face stronger winds on Tuesday.
Waikato would enjoy similar conditions to Auckland, with passing cloud and fine spells.
But the North Island’s breathing space will be brief.
The front will track north on Tuesday, bringing rain and stronger winds before moving away by the end of the day, Lynden said.
Cooler temperatures will follow, with a showery westerly flow settling in for the rest of the week. Western areas will be most exposed to those showers.
A challenging trip home
NZ Transport Agency Waka Kotahi urged holidaymakers to check weather and road reports before travelling, as heavy rain and wind could close roads at short notice.
Orange heavy rain warnings cover Fiordland, the headwaters of Otago lakes and rivers, the Canterbury lake and river headwaters about and south of Arthur’s Pass, and the Westland, Grey and Buller districts.
Rain could rapidly swell streams and rivers, trigger slips, and leave water across roads.
Orange strong wind warnings also cover Fiordland, Southland, Stewart Island, Otago and Canterbury’s high country and plains. Some warnings continue into early Tuesday.
Christchurch is also under a strong wind watch from 6pm Monday to 2am Tuesday.
Further north, Marlborough’s strong wind watch runs from 5pm today until 8am Tuesday.
Affected routes include SH1 between Picton and Kaikōura, SH6 between Blenheim and Hira, SH62 from Spring Creek to the SH6 junction, and SH63 between Renwick and St Arnaud.
On Tuesday morning Horowhenua and Kāpiti will also be under a strong wind watch.
Drivers crossing the Remutaka Hill on SH2 or the Wainui Saddle on SH1 Transmission Gully should take extra care.
Wairarapa has been upgraded to an orange strong wind warning from 5pm Monday to 8am Tuesday.
A heavy rain warning applies to Tararua Range between 2am and 11am on Tuesday, with the district also under a strong wind watch from Monday night to 1pm Tuesday.
Queenstown Lakes District away from the headwaters, as well as Southland and Stewart Island are under a heavy rain watch from 1pm to 11pm Monday.
Severe weather won’t be the only potential delay.
NZTA expects northbound SH1 traffic between Ashburton and Christchurch to be busy from 12.30pm to 6pm and advises motorists to travel outside those hours.
Motorists should avoid floodwater, where uncertain depths and hidden obstacles could make crossing dangerous.
People towing, motorcyclists, and drivers of high-sided vehicles should pull over safely if strong winds make them feel unsafe.