MetService issued a red alert, warning of severe and destructive northwesterly gales for the Canterbury High Country and foothills from 1pm today until 6pm tomorrow. Gusts of up to 160km/h in exposed places are forecast.
Earlier today 12 Air NZ flights across the South Island were cancelled due to the bad weather.
These included services in and out of Invercargill, Queenstown and Dunedin.
Impressive thunder could also be heard in the region this evening.
A video shows a grey still evening, but thunderous booms were heard.
A Cromwell resident said the evening was filled with thunder and lightning.
"Can't go 10 minutes without it," she said.
The winds are associated with a cold front moving northwards up the South Island today and early tomorrow.
Transport and power networks are likely to be significantly affected, with road closures and power outages likely, said MetService meteorologist Hordur Thordarson.
The remainder of the eastern South Island is under an orange warning, including the Canterbury Plains and Christchurch, which may suffer damaging gales from tonight into tomorrow morning.
Red warnings are reserved for only the most extreme weather events where significant impact and disruption is expected.
