On Monday, Singapore was exposed to "extreme" ultraviolet (UV) levels with the highest one-hour average UV index of 15 recorded at 1pm and 2pm, according to the Meteorological Service Singapore (MSS).

This extreme level was also recorded on Feb 13, and on Sept 8 and 17 last year.

While experts say these isolated incidents are not a major cause for concern, they also say that precautions should be taken when out in the sun, especially between 10am and 3pm, where sun intensity peaks and UV radiation is strongest.

National Environment Agency (NEA) data shows Singapore experiences high levels of UV radiation all year round, averaging 6 to 9 on the daily maximum UV Index.

Singapore's proximity to the equator puts the sun directly overhead most of the year, said Dr Abel Yang, physics lecturer at the National University of Singapore.

The UV Index - an international standard measurement of the level of UV radiation - is categorised from low to extreme.

Extra protection against sunburn is needed when values hit "very high" levels of between 8 and 10, and "extreme" levels of 11 and above, according to the NEA website.

Over the past two weeks, Singapore has experienced some of the highest UV Index values recorded, including 12 last Friday, 13 on Saturday and Sunday, 15 on Monday and 14 on Tuesday.

A high UV index means there is a larger dose of UV radiation for the same amount of time spent in the sun, said Dr Koh Hong Yi, dermatology consultant at the Singapore General Hospital.

This could lead to ailments like skin cancer, pigmentation and premature ageing of the skin in the long term.

Sun protection - sunscreen, umbrellas, hats and sunglasses - is crucial for those with fair complexions, have poorer immunity, or medical conditions such as lupus that increase sensitivity to UV, added Dr Koh.