Currently in many African, Asian and South American countries, weather reports may be available only every six to 12 hours and only for broad patches of land up to 15km (9.3 miles) wide.
But IBM's new tool provides reports down to more specific, 3km-wide areas.
The company says it can even predict individual thunderstorms.
The tool, announced at the CES tech show in Las Vegas and launched in partnership with The Weather Channel, uses supercomputers to crunch data from hundreds of millions of sensors around the globe.