Weeks of sweltering heat in Singapore saw the mercury race past 34 deg C several times in the past six weeks, and hit the second-highest temperature on record last month.

On April 1, it peaked at 36.8 deg C in Admiralty, just 0.2 deg C shy of the all-time high recorded in Tengah on April 17, 1983.

Weather experts said the Republic is not in the grips of a heatwave, adding that the temperatures seen are also not outside the norm.

But it will get hotter for Singapore and the rest of the world, with climate change making its presence felt.

Typically, the months of April and May are warmer for the country owing to inter-monsoon conditions, which are characterised by strong heating from the sun and light variable winds, said the National Environment Agency's Meteorological Service Singapore (MSS).

This week, the mercury hit 35.6 deg C in Paya Lebar and Marina Barrage between 2pm and 3pm on Tuesday, it said.

Temperatures have stayed high in recent weeks even with a natural climate phenomenon called La Nina, which has been bringing cooler and wetter weather to South-east Asia since late 2020.

Despite warmer weather due to the current inter-monsoon period, the threshold for declaring a heatwave has not been breached, MSS noted.

A heatwave in Singapore occurs when the daily maximum temperature is at least 35 deg C on three consecutive days, and the daily mean temperature throughout the period is at least 29 deg C, said MSS.

Based on past records, the nation experiences one or two heatwaves per decade, it added.

The last heatwave occurred in April 2016.

There was some relief last month with higher than usual rainfall. Despite maximum temperatures soaring past 34 deg C for nearly half of last month, thundery showers helped to moderate the overall temperature, making it the third-coolest April in the last 10 years, said MSS. About half of the island was drenched by above-normal rainfall for that month.

Weather and climate scientist Koh Tieh Yong from the Singapore University of Social Sciences said the conditions last month were within normal climatic variations.

However, soaring temperatures are expected to become a norm for Singapore and the world, he added.

"With global temperatures rising, we do expect the number of heatwaves per decade to be higher in the second half of this century," he said.

He noted that the average number of cool nights per year has fallen significantly in Singapore in the last 50 years because of local urbanisation and global climate change.

The Republic is already experiencing warming higher than the global average because of the urban heat island effect - a phenomenon of urban structures trapping heat in the day and releasing it at night.

Temperatures here have been trending 1.8 deg C higher than they were in 1948, MSS said last year.

In contrast, the average global temperature was reported last year to be about 1.1 deg C higher than in pre-industrial times, which ended around 1850.

This heat is expected to intensify within the next five years as the world faces a nearly 50 per cent chance of briefly reaching 1.5 deg C above pre-industrial levels.

That is the global heating limit set by governments and scientists as the ceiling to avoid catastrophic climate change.