MetService meteorologist Ashlee Parkes says although the peak rainfall range will remain at about 15 to 20mm an hour, thunderstorms may boost rainfall rates to 25 to 40mm/h in localised downpours.
The region is expected to receive 120 to 160mm of rain in the northern and eastern areas and about 80 to 100mm in the western parts on Monday.
"It is because the system is feeding northeasterly winds, and so Northeastern region will see more rain than the western areas," Parkes said.
Strong easterly winds were expected on Monday but would ease by the evening.
The Northeastern motion of the winds was forecasted to continue for most of the week, and similar to Monday northern and eastern areas will receive more wind.
Parkes said the wet weather would be more like periods of rain in the east and scattered showers in the west.
"It might begin to ease during the latter part of the week."
