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Singapore weather glossary

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

Forecast words

Nowcast: a very short-range forecast, here the 2-hour area forecast updated about every 30 minutes.
Fair: no significant rain expected. Still can be cloudy or hazy.
Showers: short bursts of rain, often scattered. Not necessarily island-wide.
Thundery showers: showers with lightning. Treat as a lightning event, not just rain.
Windy: notable breeze for Singapore, often during the Northeast Monsoon or a squall.

ITCZ (Intertropical Convergence Zone): the tropical rain-belt that follows the sun. Near us in Nov-Jan, further south in Feb.
Monsoon surge: a burst of stronger northeasterly wind that brings persistent widespread rain.
Sumatra squall: an organised thunderstorm line that forms west of us and crosses east, usually morning.
MJO (Madden-Julian Oscillation): a 30-60 day pulse of tropical rain that can make a wet week wetter.
ENSO / El Niño / La Niña: multi-month Pacific pattern. El Niño often means a drier Southwest Monsoon and higher haze risk.

PSI: 24-hour Pollutant Standards Index, Singapore's official air-quality headline.
PM2.5: particles smaller than 2.5 micrometres. The usual haze pollutant.
WBGT: wet-bulb globe temperature, the heat-stress metric.
UV index: sunburn-weighted ultraviolet. Extreme most clear middays here.
Rain day: a day with at least 0.2 mm of rain. Singapore averages 171 of them.

No. It describes sky cover. Rain is called out separately as showers or thundery showers.

Only a few places will see it. "Scattered" is more places. "Widespread" is most of the island.

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