The radar. Every five minutes NEA's weather radar at Changi publishes a rain-intensity image. RainRain downloads all three images NEA publishes: 70 km (≈290 m pixels) for detail over Singapore, 240 km (≈1 km pixels) and 480 km (≈2 km pixels) to cover southern Malaysia, Riau and beyond. The map always shows the sharpest one available for each area.

Your 50 m square. The map is divided into 50 × 50 m cells aligned to Singapore's SVY21 national grid. Your cell's reading is interpolated from the surrounding radar pixels (≈290 m each, the finest NEA publishes), so the answer changes smoothly as you move. You can pick a different cell size in Layers & settings.

Tracking & forecasting. Successive scans are block-matched to measure how each part of the rain field is moving. The latest scan is then carried forward along that motion (semi-Lagrangian extrapolation), with growth or decay taken from the recent trend. Uncertainty widens with lead time, which is why the forecast shows a chance of rain rather than a yes/no.

Beyond 30 minutes. RainRain follows the flow upwind across the 240 km and 480 km images to find the next band of rain headed your way and estimates when it will arrive.

Wind. The motion of rain echoes reveals the wind that steers them, typically 1–3 km above ground. It is only available while there is rain to track.

Ground clutter. Echoes that sit perfectly still scan after scan are flagged as non-weather and ignored.

Privacy. Your location never leaves your device. Place names come from a built-in gazetteer; only search text you type is sent to OneMap.

Radar data: National Environment Agency via data.gov.sg (Singapore Open Data Licence). Basemap: OpenFreeMap / OpenMapTiles / © OpenStreetMap contributors. Imagery: Esri.