Rainfall is set to arrive earlier than normal in parts of far northern Australia this year, partly reflecting the influence of the negative Indian Ocean Dipole (IOD).

The Bureau of Meteorology says northern and central Queensland and the northern NT have a 75% chance of an early onset, while the WA central west and southern parts of the Kimberley are likely to have a later than usual onset.

The northern rainfall onset occurs when rainfall totals after September 1 reach at least 50mm, which is considered the amount needed to stimulate plant growth after the dry season. It differs from the monsoon onset, which usually arrives at Darwin in the last week of December.

All climate model outlooks surveyed by the bureau indicate that negative IOD conditions are likely to continue into late spring. A negative IOD event is associated with above average winter-spring rainfall for much of Australia.

The bureau also sees a 50% chance of a La Nina forming in the Pacific Ocean later this year.