Singapore · Jun 2025 – May 2026
We checked 172,000 rain predictions against what really happened — across all five regions of Singapore, every 15 minutes, for an entire year.
The Bottom Line
The 2-hour forecast is the better one (obviously). But even that overpredicts rain.
How We Score It
Every forecast lands in one of four buckets. We care most about hits — and we ignore the easy wins.
Why ignore “correct quiet”? Singapore only rains 6% of the time. If you always predicted sunshine you’d be right 94% of the time — but useless when it matters. So we skip the easy correct-dry cases and only score the rainy moments.
Day by Day
Blue bars show how rainy each day was. The dark line tracks how accurate the forecast was — higher is better.
Each point is one day. Accuracy peaks during the Northeast Monsoon (Dec–Mar) when rain is steadier and more predictable.
By Region
Each region gets its own forecast. Some areas are simply easier to predict than others.
Score shown is 2-hour forecast accuracy. Higher is better. Singapore’s geography means a rain cell can soak one region while the next stays perfectly dry.
Time of Day
Singapore’s afternoon thunderstorms are famously sudden. The data agrees — the forecast struggles most in the afternoon heat.
Morning showers are driven by overnight convection and are more regular. Afternoon convective storms form quickly and are harder to pin down hours in advance.
By Month
When there’s a dominant weather pattern, the forecast gets better. The chaotic months in between are much harder to call.
2-hour forecast accuracy by month. The Northeast Monsoon (Dec–Mar) brings steadier rain that’s easier to forecast consistently.
Short Range vs. Long Range
The 2-hour forecast wins on every measure. The further ahead you look, the more uncertainty piles up.
Compared over the same 6am–midnight window to keep it fair. The 24-hour forecast over-warns — it plays it safe by predicting rain too often.
About This Analysis
Real rainfall readings from Singapore weather stations, plus 2-hour and 24-hour forecasts from the national weather API. June 2025 to May 2026, every 15 minutes.
A 15-minute window is called rainy if the total across all stations in the region hit 1 mm or more. The forecast “predicted rain” if the descriptor mentioned showers, rain, or thunder.
Critical Success Index only counts the interesting moments: hits, misses, and false alarms. It ignores the many easy “correctly dry” windows. It is the standard metric in weather verification science.
The 24-hour forecast only runs 6am–midnight. To compare fairly, we matched the 2-hour forecast to that same window — not the full 24 hours.