‘Aircon weather’ in Singapore: What’s behind the rainy, cool week?

Mr Darroy Xie, 25, who works in the hospitality industry, also had his Chinese New Year plans disrupted because of the rain. On Wednesday, the second day of the celebration, he was late for a family dinner because it was difficult to book a taxi.

However, he noted that the rain “makes it like aircon weather”.

CNA looks at what is causing this “aircon weather”, is it unusual and how long can we expect it to continue?

WHAT’S BEHIND THE COOL, RAINY WEATHER?

Experts said that the recent wet spell is due to a combination of regional climate forces.

First, the ongoing La Nina phase.

Assistant Professor Wang Jing Yu from the National Institute of Education (NIE) said that the heavy rain and cool temperature are mainly due to an ongoing La Nina weather pattern.

During La Nina, sea surface temperatures in the western Pacific become warmer than usual, leading to increased evaporation from the ocean, he said.

“This surge in water vapour enhances cloud formation and subsequently results in more intense and frequent precipitation,” Asst Prof Wang said.

According to the Met Service, Singapore is currently under moderate La Nina conditions. The country last experienced La Nina in early 2025.

Next, the Madden-Julian Oscillation (MJO).

Professor Steve Yim from Nanyang Technological University (NTU) attributed the heavy rain and cooler temperatures to the MJO over the Maritime Continent, which is a large-scale atmospheric system.

The US National Oceanic and Atmospheric Administration (NOAA) describes the phenomenon as an eastward-moving disturbance of clouds, rainfall, winds and pressure changes. It travels through the tropics and typically cycles back to its original starting region every 30 to 60 days.

The current MJO phase has reinforced an upward motion near Singapore, amplifying the rainfall intensity and extending the wet spell, said Prof Yim.