A heavy rain warning has been issued for the Hawke's Bay ranges.
The warning was upgraded from a watch this morning.
The heavy rain will particularly affect the Kaweka and Ruahine ranges.
The rain has started in some areas of Hawke's Bay will gradually worsen becoming persistent in the afternoon MetService Meteorologist Stephen Glassey said.
The warning begins at 4pm today and will last until 3pm Friday.
Glassey said the rain in the Kaweka and Ruahine areas will measure between 100-140mm in 24 hours.
In other parts of the ranges, the rain will measure between 70 and 90mm.
At its peak, the rain will intensify to 10-15mm an hour.
All areas of the region will experience substantial rain but further inland and coastal areas will have between 20 and 30mm.
Glassey said this is one of the more significant events in recent times for Hawke's Bay but is not extreme for this time of year.
At Napier Airport rain recorded is only half of the usual average for this time of year he said.
However, due to 26.6mm measured on June 1, 13.6mm on June 21 and other less significant periods of rain, rain is measuring at the average.
Friday's rain may bring the record above average for the month.
MetService have also said that the heavy rain may cause streams and rivers to rise rapidly and surface flooding and slips are possible.
Hawke's Bay Civil Defence Emergency Management Group manager Ian Macdonald said this is not unusual for the ranges, but people should drive to the conditions and keep up to date with weather warnings.
The rain will begin to ease early on Sunday.
There have been a few lightning strikes further north, but as the weather system moves south the conditions for lightning are reducing, he said.