A big low out in the Tasman Sea is looking pretty significant but it is going to weaken and fall apart before it reaches New Zealand - due to a big blocking high to our east.

The low will unravel and dump areas of very heavy rain, but also lighter drizzle, says WeatherWatch.co.nz.

Winds will be blustery for a time and while not likely to be damaging for most it could make camping in a tent a bit uncomfortable for the next 48 hours. 

"There's also some risks of minor damage to crops due to strong winds - but again damage shouldn't be much," warns the weather organisation.

"Humidity and rain are probably the main factors to watch, with sub-tropical air combined with daytime heating to boost the rain-clouds further. Humid air flows like this can create low cloud, drizzle and sudden heavy downpours, especially northern facing areas."

Western and northern facing regions of both islands may have heavy downpours, especially on Thursday as the remnants of this low move in.

The low falls apart by Friday.

WeatherWatch.co.nz says a cooler change arrives in the Central Otago area on Thursday with a chance of rain and a 10 degree drop in daytime highs for Central Otago and a drop of over 13 degrees in Southland.

'There's also a chance of rain for Southland on Thursday - very welcome news to those dealing with near drought conditions."