The strongest El Niño on record is not the same as the worst summer on record
There is a very large El Niño building in the Pacific, and for once the coverage is not overstating the scale of it.
The Bureau of Meteorology has the event firmly established, with its Relative Niño3.4 index sitting at +2.45°C against a threshold of +0.80°C. The World Meteorological Organisation has called it very strong and put the likelihood of it lasting through February 2027 at close to 100 per cent.
The WMO also said something forecasting agencies rarely say about their own work: this was the first time one of its El Niño updates had been so unequivocal.
The Southern Oscillation Index has fallen to nearly −30, well past the −7 threshold that qualifies an event. Climate scientist Daniel Swain puts the odds of this becoming the strongest event on record since at least 1950 at around 70 per cent.
A bigger El Niño doesn't scale up your summer the way you'd expect
The relationship between El Niño's strength and Australian rainfall flattens out quickly. According to modelling reported by the ABC's meteorologist Tom Saunders, drawing on the Bureau's ACCESS-S system, Australia collects most of the drying effect once the Niño3.4 index passes about +0.8°C.
Beyond that point, extra strength does a great deal to the odds of record global temperatures and comparatively little to our rainfall.
Saunders puts it plainly: El Niño's impact on Australia's weather often has little to do with its strength. Weak events have produced severe droughts. Strong ones have occasionally produced very little.
Two other details matter here: El Niño's influence on Australian rainfall is weakest in summer, which is the exact season everyone is discussing. And the last El Niño, in 2023–24, delivered eastern Australia an above-average summer of rain, driven more by the Southern Annular Mode and unusually warm oceans than by the Pacific pattern. This year has followed a similar script so far: Rainfall through winter and early spring has run well above what a textbook El Niño would predict.
Treat this as a reason to be precise about where your confidence sits. The heat carries the higher confidence and the rainfall carries far less.
One more point worth making clearly, because it's the comparison everyone reaches for: This season differs from 2019 in an important way. Most of the country is not sitting in the long, severe drought that preceded Black Summer.
What really deserves your attention
The heat, and what it costs you. This is the part of the forecast you can plan against with reasonable confidence, and it's the part businesses plan for least, since heat arrives gradually and rarely produces a dramatic photo.
It also lands unevenly. Penrith Lakes has a long-term January mean maximum of 30.8°C. Sydney's Observatory Hill sits at 26.0°C, nearly five degrees cooler. That gap exists every year, before any heatwave is even declared. Last January, Western Sydney spent several days above 42°C while the city centre stayed several degrees cooler on the same days. A forecast written for Sydney describes a different Tuesday than yours.
That matters here more than most places, since 28.7 per cent of the Hawkesbury's 7,823 registered businesses are in construction. Close to three in ten of us do outdoor work.
There's a compliance angle many small operators haven't looked at. SafeWork NSW treats extreme heat as exposure above 30°C and/or high humidity, and employers carry a duty to eliminate or minimise that risk so far as is reasonably practicable, in consultation with workers. Workers can refuse work where they reasonably believe it exposes them to a serious risk. Australia has no legislated maximum working temperature, which surprises people, so the 30°C figure works as an indicator rather than an automatic stop.
The useful move is deciding, now, who calls it, at what point, and who rings the client. Businesses that settle that in November don't have to negotiate it at 11am on a 41-degree Tuesday with a customer on the phone.
Your sum insured, which has quietly gone stale. The Insurance Council's Catastrophe Resilience Report 2025–26 puts the cost of building a standard Sydney home at $350,000 in 2021, rising to $491,000 by 2026, a jump of just over 40 per cent against 24 per cent CPI growth over the same window. Roof tiles alone are up 77 per cent in five years.
Nobody chose to be underinsured. It happened to a great many businesses through renewing on autopilot. Three questions worth asking before December: is your sum insured based on current rebuild costs, does your policy treat flood and stormwater differently, and do you have business interruption cover and for how long?
Water, even in a dry season. A dry forecast doesn't mean a dry day, and hard, dry ground sheds water rather than absorbing it. Sydney's Observatory Hill recorded 126.8mm on 18 January this year, its highest daily rainfall for the month since 1988, in what was otherwise a season running below the long-term average. Getting stock off the floor and gutters cleared costs little and covers a bad afternoon.
The paperwork, which is duller and more decisive than any of it. If your ABN registration lists a PO box rather than a physical address, that can affect your eligibility for government disaster assistance. Keep records backed up somewhere other than the premises. Build a contact list that includes your insurer, your bank, your suppliers and your staff, one you can reach without the office. It's an afternoon's work, and none of it depends on knowing what the weather will do.
Be Bushfire Ready, in advance*. Check whether your home and business are in a bushfire-prone area
Make an emergency action plan with your staff
Complete a Bush Fire Survival Plan
Look after the property around your premises
Save your trusted information sources
The part of your plan you cannot buy
Most business continuity guides quietly assume you'll solve the problem alone: cold storage, a generator, a room with working air conditioning, a van, somewhere dry to put stock, somewhere to sit and take calls.
Almost none of that needs to be purchased and most of it already exists within twenty minutes of you, owned by someone you've already met. The NSW SES says plainly that it may not be able to rescue you during storms. That's not an institutional failure. It's arithmetic. In a widespread event, resources go to life safety, and your business isn't the priority. The honest question becomes who you know, and whether the two of you have actually agreed anything.
So make it specific, name three businesses: one with space you could borrow, one with equipment you'd need, and one that could look after your customers for a fortnight if you couldn't. Then ring them, agree in both directions, and write the mobile numbers somewhere that isn't your phone.
The Hawkesbury Valley has flooded eight times since 2020, so this isn't theoretical for anyone reading it. The businesses back on their feet fastest were rarely the best insured. They were the ones with somewhere to go and someone to call. Widening that network before you need it is the whole argument, since an arrangement made in November is a plan, and the same conversation attempted in January is a favour, harder to ask for when everyone's having the same week you are.
None of this depends on knowing what the summer will do, which is fortunate, since the Bureau's summer outlook isn't published until late November. By then, most of the preparation worth doing should already be behind you.
The network is the only part of the plan that gets stronger the more people use it. Everything else on this list depreciates.
Citations
Bureau of Meteorology, Climate Driver Update, 1 September 2026
WMO, El Niño set to become very strong, 3 September 2026
ABC News, What a super El Niño means for Australian weather, 15 April 2026
ABC News, Record El Niño to bake Australia, 31 July 2026
ABC News, Why Australia's weather is seeing a soaking while a record El Niño is forming, 22 August 2026
Bureau of Meteorology, Australian rainfall during El Niño and La Niña events
Bureau of Meteorology, climate averages, Penrith Lakes AWS
Bureau of Meteorology, Sydney in January 2026
Insurance Council of Australia, Catastrophe Resilience Report 2025–26
economy.id, Hawkesbury businesses by industry (ABS, 2024)
SafeWork NSW, managing extreme heat at your workplace
NSW SES, Storm Season
NSW Reconstruction Authority, Hawkesbury-Nepean Valley Disaster Adaptation Plan fact sheet, November 2024
https://www.nsw.gov.au/emergency/bushfire/prepare/your-business*