Tropical Cyclone Donna passed just to the west of Vanuatu over the weekend bringing flooding rains and damaging winds. The storm is now in the process of drifting just east of New Caledonia.

The winds may have eased significantly, but it is still capable of causing extensive damage and widespread flooding is inevitable.

At its strongest, Donna's winds reach 215 kilometres an hour with gusts of up to 260km/h. That made it equivalent to a Category 4 Atlantic hurricane on the Saffir-Simpson scale.

In doing so, Donna become the strongest tropical cyclone ever recorded during the month of May in the southern hemisphere. It surpassed the power of Cyclone Nadu way back in 1986.

It is all the more remarkable that a storm of such intensity should develop this late in the season, which officially ended on April 30.

No doubt this unusual event would have earned a mention at the climate change conference taking place in Bonn this week.

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The storm has been allowed to steadily gather strength because it has not made landfall. As such it has kept its feed of warm moist air over the waters of the southern seas.

This constant water source means that it has brought incredibly wet weather to Vanuatu. The village of Sola on the island of Vanua Lava had 147mm of rain on Friday ahead of the storm. By the end of the weekend it notched up 395mm.

Further south, Bauerfield Efate recorded 191m of rain on Sunday alone. The worst of the rain is now moving towards, but not directly across New Caledonia.

Donna currently lies about 250km to the northeast of New Caledonia's capital city, Noumea. Winds are still touching 165km/h with much higher gusts.

That is still equivalent to a Category 2 hurricane, but it should weaken quickly over the next 12 hours and be downgraded to a tropical storm by the early hours of Wednesday local time.

Flooding is still likely across New Caledonia in the short term, but 24-hour rainfall totals are now nearer 70-80mm. The storm will clear by the end of Wednesday and the remnants of the storm will bring heavy rain to northern fringes of New Zealand by the weekend.