With the scorching Blenheim temperature, Fire and Emergency NZ has lifted the fire danger warning at Marlborough's Wither Hills Farm Park to "extreme".
All of the park, except for the lower tracks, are closed, the Marlborough District Council said.
In the North Island, Gisborne wasn't far behind, with a sweltering high of 35C.
It was a similar story today in Masterton, with a peak of 34C, but the temperature will be back in the mid-20s tomorrow.
As residents baked under the sun yesterday, Canterbury DHB emergency department clinical director Dr David Richards said "a number" of the 292 admissions yesterday would've likely been heat-related, such as dehydration and confusion.
'Tinder dry' but relief on the way
Fire and Emergency NZ's Response Co-ordinator Colin Russell told Chris Lynch on Newstalk ZB firefighters have been in a heightened state of awareness due to the weather.
"Today's [Wednesday] our touchpoint. It's really tinder dry and very volatile out there today.
"It does surprise people how fast fire can move, and when the conditions are dry the fire can travel extremely fast."
But relief is on the way for sweltering South Islanders.
MetService forecaster Sonja Farmer said the temperatures will dip a few degrees today before a chill sets in from tomorrow.
In Timaru, cloud was already starting to strip the heat, with the temperature dropping by nearly 10C from the 33.2C recorded at 11am.
2⃣:3⃣0⃣ pm 🌡
Toasty temps across the eastern seaboard this afternoon, but cloud is already starting to strip towns of their heat. Timaru has dropped nearly 10°C from 33.2°C at 11am. Watch out next #christchurchhttps://t.co/Yjbq0jxdqz ^Tahlia pic.twitter.com/dU0YigW8Lm
Christchurch is expected to reach a high of 22C tomorrow with morning rain and isolated showers throughout the day.
Fire permits have been suspended in most of the South Island.
Permits are granted when an area is in a restricted season, and have been suspended indefinitely in Canterbury.
They have also been suspended in the Nelson District with the exception of Nelson Lakes, Murchison, and Golden Bay West for 48 hours.
Fire and Emergency NZ's response co-ordinator Colin Russell said with the high temperatures and strong winds forecast, cancelling active fire permits reduces the potential for fires getting out of control.
"Please, avoid any spark-generating activities, like grinding and cutting metals outdoors, or using farm machinery. Even mowing the lawn could cause sparks to start an out-of-control fire. Also check previous burn sites for hot embers and if you see a fire call 111 immediately.