El Nino Winter: What It Means on the Water

Plan your season around the BOM outlook

BOM senior climatologist Caitlin Minney confirmed on 21 May that both day and night temperatures are "very likely" to be above average across Australia for the June-August period.

The Bureau of Meteorology's winter outlook, released 21 May 2026, tips below-average rainfall for south-west Western Australia, Victoria, parts of SA and southern NSW, driven in part by an El Nino that hasn't officially formed yet but is tracking that way.

"For July, that's where we start to see that dry signal emerge across parts of the south and the east, with early indications of a strengthening of that signal into August," Minney said.

The oceanic indicators for El Nino are well advanced; atmospheric indicators are catching up.

This matters for anyone planning time on or in the water between June and August.

Why El Nino changes the water, not just the air

El Nino begins in the tropical Pacific, where warmer-than-normal sea surface temperatures weaken the trade winds, causing the eastern Pacific to warm further.

That shift re-patterns the subtropical jet stream across the southern hemisphere, which in turn affects where rain-bearing frontal systems track through Australia.

For southern Australia, the result is fewer deep low-pressure systems penetrating the mainland during winter - which means fewer stormy windward days and more settled windows for water activities.

It's a counter-intuitive point: less rain in an El Nino winter often means more usable days on the water, even if big swell events are harder to find.

"Snow levels can change rapidly based on just one strong frontal system - and so can swell."

Caitlin Minney's observation about the snow season applies equally to surf: one deep low from the Southern Ocean can still produce several days of solid swell even in a suppressed El Nino pattern.

What it means for surfers

El Nino winters typically reduce the frequency of deep Southern Ocean lows that generate the long-period swell southern Australia runs on.

Expect fewer back-to-back swell events in June-August 2026 compared with recent La Nina years, with longer flat spells between decent surf.

When the swell does arrive, the quality is often cleaner - El Nino winters in southern Australia correlate with more offshore high-pressure ridges, which smooth out the surface and improve form.

The trade-off is frequency: you'll need to track forecasts tightly rather than assuming there'll be surf this weekend.

For eastern Australia, the reduced tropical cyclone activity that comes with El Nino also means less generated north swell for QLD and northern NSW breaks during what is already a swell-quiet season.

Set your swell alerts to 8-second-period or more so you catch the quality events when they do arrive this winter.

What it means for fishing

This is where an El Nino winter works clearly in your favour.

Below-average rainfall across south-eastern Australia means reduced freshwater runoff into estuaries and bays through winter.

Lower runoff keeps salinity higher and water clarity better - which is good news for targeting reef species, snapper and flathead in clearer water close to shore.

Warmer-than-normal sea surface temperatures, which BOM is forecasting for the season, push the thermal boundary southward.

Species that would ordinarily move north in winter - yellowfin tuna, mahi-mahi and longtail tuna along the east coast - may hold in southern latitudes longer than usual in 2026.

The flip side is that the same warmer conditions can compress the thermocline, pushing bait schools deeper and making sounder work more important for targeting pelagics.

For estuary and bay fishing, expect better visibility through June and July in systems like Sydney Harbour, Port Phillip Bay, the Broadwater and the Swan River as freshwater input stays low.

What it means for sailors

An El Nino winter pattern across southern Australia typically means more high-pressure influence - which translates to more consistent sea breezes, less of the frontal nastiness that shortens sailing windows.

For weekend sailors in southern states, this means more structured afternoons with predictable thermal winds than you get in a wet, frontal La Nina winter.

Perth sailors will already know the Fremantle Doctor well, but note that south-west WA faces the strongest dry signal this winter, meaning offshore runs and overnight passages may see lighter conditions than usual.

For passage planning in June and July, watch for the occasional deep low that does push through - Minney's point about one system changing an entire season applies to offshore sailors as much as snowfields.

The advantage: longer, drier windows between systems make passage timing more predictable than a La Nina season.

What it means for divers

Clear water and less runoff are the big wins for divers this winter.

In Port Phillip Bay, Sydney Harbour and the Whitsundays, horizontal visibility in winter typically improves as river flow drops - and BOM is forecasting a dry June through August across most southern diving regions.

Warmer sea temperatures mean wetsuits stay at 5mm rather than 7mm for most of the east coast through July, which extends dive time and reduces fatigue on multi-dive days.

The structural change worth knowing: warmer surface water in an El Nino year can reduce upwelling intensity along parts of the south-east coast.

That matters because upwelling drives nutrient delivery to reef systems - in a strong El Nino year, some reef areas can see reduced biological activity as the cold, nutrient-rich water stays deeper.

For the typical sport diver, this is a minor concern; for spearfishers targeting reef fish aggregations, it's worth factoring into your spot selection in August.

Planning your season

The practical summary: June and July are likely to be your best windows for anything that depends on settled weather - offshore fishing, sailing passages, diving in southern states.

For surfers, the better approach is to stay flexible and check the forecast 3-4 days out rather than pre-booking sessions around calendar dates.

August is where BOM's dry signal strengthens most; if you're planning a surf trip to Margaret River or a diving trip to the Great Barrier Reef, August 2026 looks like a strong bet for settled conditions.

Keep an eye on the weekly BOM ENSO update for any shift in El Nino status - if the pattern strengthens faster than expected, southern swell frequency could drop further while northern diving and fishing improves.

Use Seabreeze's 7-day wind forecasts and tide charts to pick the windows when they come this winter.

Questions for your winter planning

Will there be any surf at all? Yes - El Nino suppresses frequency, not all swell. Southern Ocean systems still track north through winter; they're just less frequent and less stacked than La Nina years.

Should I change my fishing tackle setup? In clearer water, drop to lighter leaders and smaller profiles on lures. For pelagics that may hold further south, have longer run lines and a sounder ready to locate the thermocline.

What should sailors watch most closely? The occasional deep low that breaks through the pattern. Even in suppressed El Nino conditions, one strong frontal system can catch you out if you've got complacent about checking forecasts.

How does this affect the Great Barrier Reef? Warmer water is a bleaching risk; the GBR has faced bleaching in past El Nino years. Current BOM forecasts don't confirm a severe event, but it's worth watching Reef Authority bulletins if you're planning a dive trip north.