A spate of tropical sea snakes washing up along the New South Wales south coast after recent wild weather seems to be part of a global trend – and weather pattern.

Carolyn Larcombe, from Burra near Canberra, spotted a small yellow-bellied sea snake on the sand while walking along Congo Beach, 10km south of Moruya.

She told the ABC the snake was “very quiet” and that, using a stick, she was able to manoeuvre it into the water. She did the same with a second, larger, snake of the same species she found later that day.

The species is highly venomous but not typically aggressive.

“I’m not scared of snakes; I was being very, very careful,” Larcombe said. “I thought they had a better chance of survival back in the water than up high and dry on the sand.”

One other sea snake stranded in the same area had been reported to the animal rescue organisation Wires.

Yellow-bellied sea snakes are found within a few kilometres of coastlines the world over, including much of Australia. They prefer shallow inshore waters of between 11.7C and 36C, but can be found in the open water well away from coasts and reefs.

They are entirely aquatic, so being stranded on land is often attributed to sickness, injury or ocean turbulence caused by strong winds or storms.

The highly venomous yellow-bellied sea snake is usually found in the tropics, but weather conditions sometimes bring them to cooler coasts. Photograph: Wandiyali Images

Wires reptile expert Gary Pattinson said for this reason beachings tended to happen in spates.

“They generally live their whole lives at sea,” he said. “When they’re getting washed up, it’s generally a good sign there’s been extremely stormy weather or the snake itself is injured or sick. Weaker snakes will get tired – they don’t have the strength to fight the ocean.”

In more than a decade of working with reptiles, Pattinson had encountered only five or six sea snake strandings. They were “very, very beautiful animals – and very placid as well”.

Though stranded snakes were invariably “the weaker of the bunch”, he encouraged people to “throw them back in”.

An unprecedented number of sightings of yellow-bellied sea snakes reported in California at the end of last year – further north than the species tends to be found – was attributed to warmer ocean temperatures triggered by the El Niño weather pattern.

Snakes were found washed up on Silver Strand beach in southern California in October for the first time in three decades.

This year’s El Niño in the Pacific is now one of the three strongest recorded. Australia’s Bureau of Meteorology found in November that sea surface temperatures in the central and eastern tropical Pacific were 2.4C above average.

Yellow-bellied sea snakes were last spotted in California in 1972, during another El Niño, said Greg Pauly the curator of Herpetology at the Natural History Museum of Los Angeles County, who retrieved both snakes in October.

Pattinson said changes in ocean temperatures would affect reptiles, which rely on their environment to control their body heat.

“You would expect to see some sort of anomalies in their behaviour,” he said. “It wouldn’t surprise me, especially if coupled with that there was rough weather, that you would see a mass beaching.”

Last month, the critically endangered short-nosed sea snake, thought extinct, was rediscovered off the West Australian coast when two were photographed mid-courtship.

• This article was amended on 8 January 2016 to correct the date yellow-bellied sea snakes were previously spotted in California from 1983 to 1972 and to attribute that to Greg Pauly.