Weather guides

The radar shows where rain is now. The 2-hour nowcast is the forecast. Use both, plus the colour scale, to decide if you need an umbrella in the next 30 minutes.

Singapore's headline air number is the 24-hour PSI. The 1-hour PM2.5 reading tells you what the air is doing right now. They answer different questions.

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.

WBGT folds temperature, humidity, sun and wind into one number. In Singapore humidity is the reason a 32°C day can be harder than a drier 36°C day elsewhere.

December to early March. Wet and cool at first, then often dry and windy. This is when Singapore sets rainfall records and also enjoys some of its clearest skies.

June to September is generally drier, but 4am thunderstorms and transboundary haze are the two things that catch people out.

Light winds plus strong sun. Storms grow over the island in the afternoon, and lightning days peak. May is the hottest month. November is one of the wettest.

A warning is not a forecast flavour. It means a specific hazard is happening or is expected soon. Treat flood and lightning the most seriously.

If you can hear thunder, you are in range. Wait 30 minutes after the last thunder. November is the peak lightning month.

Haze is a wind-and-fire problem, not a local one. Watch PSI and 1-hour PM2.5, not just the colour of the sky.

Singapore floods are usually short, local, and driven by intense rain on a small urban catchment. Do not drive into the water.

Check five things before you keep a group outside: lightning, heat stress, UV, air quality, and whether rain is a cell or a surge.

A plain-language glossary for the words that show up on forecasts, radar and air-quality pages.

Singapore has mixed tides that vary by coast. A high spring tide plus a rain surge is when coastal and river-mouth flooding gets ugly.