Australia is heading into a hotter and in many areas wetter summer, with the Bureau of Meteorology warning of an elevated risk of flooding and fire as temperatures climb.

The Bureau’s long-range outlook for the final months of 2025 points to above-average rainfall across much of the eastern half of the country, especially in northern Queensland as the wet season builds. At the same time, warmer-than-usual days and nights are expected nationwide.

That combo of wet ground and rising heat creates a double-edged risk. The BOM says saturated soils and near-full water storages in the east raise the chance of flooding over summer, while prolonged warmth in the south-east and Kimberley heightens the threat of bushfires and heatwaves.

Meanwhile, on the mercury, “daytime temperatures for October to December are likely to be above average across most of Australia,” the agency said. “Minimum temperatures are also very likely to be above average across the country.”

For farmers, the BOM’s outlook means a summer of mixed blessings and high stakes. While above-average rainfall in the east and north could support strong pasture growth and refill dams, it also brings a heightened risk of crop losses from flooding and makes harvest timing more unpredictable. In the south-east and parts of Western Australia, the increased fire risk and expected heatwaves will keep growers and graziers on alert for both water security and asset protection.

The forecast notes that September brought record rainfall in parts of the north and east. Cairns notched its wettest September ever, while Sydney recorded its soggiest September day since 1879. But other regions remain parched, with central Victoria and sections of south-eastern Australia still showing severe rainfall deficits.

For investors and businesses, the BOM’s data suggest continued volatility in weather-sensitive sectors such as agriculture, insurance and energy. Above-average rainfall can boost pasture growth and dam levels in Queensland and New South Wales but complicate grain harvests and transport. Prolonged warmth tends to lift electricity demand and pressure grid reliability.

Looking slightly further ahead, the November–January outlook reinforces the theme: warmer-than-average conditions are likely almost everywhere, with only northern Australia showing a clear signal for heavier rainfall. The Bureau says the Pacific’s El Niño–Southern Oscillation remains neutral, though a La Niña event could still develop in spring, while a negative Indian Ocean Dipole is already contributing to higher rainfall across southern and eastern Australia.

New model to better track potential extreme El Niño and La Niña events

The BOM recently announced a pretty major change to how Australia’s weather is tracked, with a new method for measuring the climate patterns known as El Niño and La Niña. As a reminder, El Niño and La Niña are naturally occurring climate patterns in the Pacific Ocean that shift ocean temperatures and winds. El Niño will bring hotter, more dry conditions, while La Niña offers cooler and wetter periods.

Starting in September 2025, the Bureau now uses what it calls the “relative Niño index” to track the El Niño–Southern Oscillation (ENSO). That's what basically governs the El Niño/La Niña cycle, bringing either big rains or serious heatwaves and potential droughts.

Why the change? 

In short: it's climate change-driven. As global oceans have warmed over the decades, traditional ways of measuring ENSO (where meteorologists would compare Pacific Ocean temperatures to an historical average) have become less reliable. 

The Bureau explains: “The traditional Niño indices show how warm certain regions are, but they don’t account for the long-term warming trend. If we don’t account for the warming, El Niño may seem more common and La Niña may seem less common” .

The new relative Niño index solves this by measuring how unusually warm (or cool) the Pacific is compared to other tropical oceans.

“Assessing how unusually warm or cool the ocean is compared to the broader tropical areas gives us a clearer picture of how the ocean and atmosphere interact to reinforce each other,” the Bureau says.

What difference does it make? 

For the average reader, it means Australia’s climate forecasts now more accurately reflect genuine shifts in ENSO, not just the creeping background of a warming ocean. In practice, this should lead to more accurate tracking of weather extremes and better comparisons with past El Niño and La Niña events—crucial for everyone from farmers and insurers to investors and policymakers.

The Bureau stresses the thresholds for declaring an El Niño or La Niña event remain unchanged, and the overall record of historical ENSO events is largely unaffected. The new model did prompt a reassessment of two recent weak La Niña events, but for the most part, past events remain consistent.

For those who prefer the more retro model, the BOM says the old index is still available for those who'd rather use that. But “by using relative Niño indices we are improving our capacity to monitor ENSO and provide clearer and more reliable insights into climate patterns,” the Bureau says.

Other international weather agencies are now reviewing the science behind the new approach, with growing recognition that the relative Niño index can help the world keep pace with a changing climate.