5 min read

UV index in Singapore: why noon is Extreme most days

Near the equator the midday UV index is Extreme on most cloud-free days. Shade, sleeves and SPF matter more here than in temperate cities.

The scale

  • 1-2 Low
  • 3-5 Moderate
  • 6-7 High
  • 8-10 Very High
  • 11 and above Extreme

In Singapore the index commonly reaches 11 to 13 around solar noon on a clear day. Clouds cut it sharply. A thick thunderstorm anvil can drop UV from Extreme to Low in minutes, which is why the live reading swings so hard around 2pm to 4pm.

Why Singapore is different

At 1.3°N the sun passes nearly overhead. Day length barely changes through the year, so there is no "weak winter sun" the way there is in Europe or North Asia. February and March often have the most sunshine hours. November and December have the least, because of monsoon cloud, not because the sun is lower.

A practical daily plan

  • Before 9am and after 5pm: UV is usually Moderate or lower. Best window for long outdoor sport.
  • 10am to 3pm: treat uncovered skin as a risk even if it does not feel burning hot. Heat and UV are not the same.
  • Water, sand and concrete bounce UV. A marina or stadium can feel worse than a park with trees.

Questions

Does SPF 50 block Extreme UV?

It blocks a high fraction of UVB if applied well and reapplied. It does not replace shade or clothing, and it does nothing for heat stress.

Is a cloudy day safe?

Thin high cloud still lets a lot of UV through. Only a thick, dark storm cloud reliably knocks the index down.

Independent guide based on publicly described NEA and Meteorological Service Singapore products. Not affiliated with NEA.