"Make sure you pick a spot that you can easily leave from should waterways begin to rapidly rise.
"Let someone know where you are going and how long for and take appropriate gear, clothing and food."
In an emergency call 111, if something has already happened call 105 or report it online at 105.police.govt.nz.
But for the rest of the country it's shaping up to be a dry New Year's Eve tomorrow.
The top of the country looks set to be the warmest place to farewell 2020, with a high of 25C and a low of 14C predicted for Whangārei - although there could be a few showers in the afternoon.
Auckland is not far behind, with a high of 24C and a low of 15C.
From Wellington up the west coast and through the central North Island there was expected to enjoy fine weather all day, although the temperatures were likely to sit slightly lower at about 22C.
Around the country the forecast for tomorrow is for fine weather for most parts, however the West Coast may see some patchy rain later in the day while inland parts of Southland, Otago and South Canterbury could see downpours developing and turning to rain overnight, according to Weatherwatch.
It could be a wet night for those heading to Rhythm and Alps, with rain predicted to set in tomorrow evening around Wanaka.
In the North Island, the day might start with a few patches of drizzle around Gisborne and coastal Hawke's Bay but it should clear by evening.
The New Year's Eve forecast
Whangārei: Fine, but chance of a shower in the afternoon or evening. High 25 degrees, low 14 degrees.
Auckland: Mainly fine. Light winds. High 24C, low 15C.
Tauranga: Fine. Light winds and sea breezes. High 23C, low 14C.
Napier: Cloudy periods. A few showers, clearing during the morning. Southerlies dying out in the afternoon. High 21C, low 12C.
New Plymouth: Fine. Light winds. High 21C, low 12C.
Wellington: Morning cloud, then fine. Southerly breezes. High 20C, low 13C.
Nelson: Some morning cloud, then fine. Cloud returning in the evening. Light winds. High 20C, low 13C.
Christchurch: A mostly cloudy day but some afternoon fine breaks. Fresh northeasterlies. High 19C, low 11C.
Queenstown: Mostly cloudy. A few showers from afternoon, some possibly heavy. Light winds. High 22C, low 13C.
Dunedin: A mostly cloudy day with a few showers from afternoon. Northeasterlies. High 20C, low 13C.