Warm Tasman Sea affecting weather in eastern NSW

Abnormally warm water in the Tasman Sea is affecting the weather in eastern New South Wales, insulating Sydney and making beach swims an ongoing option despite being less than three weeks away from winter.

The East Australian Current (EAC) – a southward-flowing ocean current that transports water from the Coral Sea down the east coast of Australia – has caused several large pools of unusually warm water to develop in the Tasman Sea this month. These warm pools, also known as eddies, contain water that is around 2 to 4°C warmer than average for this time of year.

Sea surface temperature anomalies near Australia on May 11, 2026, showing areas of abnormally warm water in the Tasman Sea
Image: Sea surface temperature anomalies during a 6-day period centred on May 5, 2026. The red areas show where sea surface temperatures are more than 2 °C warmer than average for this time of year. Source: IMOS.

Warmer-than-normal water is extending south from NSW towards eastern Victoria and Tasmania. According to data from Australia’s Integrated Marine Observing Sydney (IMOS), water temperatures in much of the western Tasman Sea are currently in the top 10% of historical records for this time of year.

This warm water is influencing the weather over eastern Australia. Higher ocean temperatures cause air sitting just above the ocean’s surface to also become warmer. When onshore winds blow this maritime air towards land, it directly affects the air temperature in cities and towns along the coast.

Daytime maximum temperatures in Sydney have been running around 2 to 4°C above average since late last week. Despite a brief cold snap earlier this month, the running average temperature during the first 13 days of this month have been more than 3°C above average, making this Sydney’s warmest start to May in 8 years.

This week’s onshore winds are also carrying moisture-laden air from the warm Tasman Sea, resulting in showers along the coast and ranges.

Image: Showers streaming over the NSW coast on Wednesday, May 13, 2026. Source: Weatherzone.

Water temperatures at the beaches are also a bit warmer than usual for this time of year, making it more pleasant than usual for swimmers and surfers.

Looking ahead, relatively warm and showery weather will continue in eastern NSW for the rest of this week. Sydney will continue to see daytime maximum temperatures around 22 to 24°C, hovering a few degrees above the May average of 19.6°C.