Police are arming themselves with wet weather gear and reports of surface flooding around the region are already pouring in.
MetService’s Severe Weather Warning for Nelson and the Richmond Ranges is beginning to take affect.
The warning is for a period of significant and intense heavy rain, expected from midday Monday through to 3 am Tuesday.
It is forecast that 100 to 150mm is likely to accumulate in the ranges, while 50 to 90mm could accumulate in some lower lying areas. Maximum rainfall intensities of 25 to 35 mm/hr from Monday night.
This amount of rain will cause streams and rivers to rise rapidly, slips and surface flooding, and could make driving conditions hazardous.
It is recommended that people be prepared for this heavy rainfall and be vigilant, especially around rivers and streams.