Data Sources

Here's exactly where the weather information on Tomorrow Weather comes from, and how it reaches your screen.

Weather forecasts and current conditions

Forecasts and live conditions are provided by Open-Meteo, an open-source weather API. Open-Meteo combines numerical weather prediction models from national weather services — such as NOAA (United States), DWD (Germany), ECMWF (Europe), Météo-France, the Japan Meteorological Agency and others — and selects the best available model for each location.

What we show from it:

• Current conditions — temperature, "feels like" temperature, relative humidity, wind speed and the weather condition;
• Daily forecast — high and low temperatures and the expected condition for today plus the next days, including tomorrow;
• Sunrise and sunset times for the selected place.

Place search

City search and autocomplete use the Open-Meteo Geocoding API, which is based on the GeoNames database. If you use "Use my location", your browser provides your coordinates directly for the weather request — see our Privacy Policy.

Weather conditions and icons

Condition labels ("Partly cloudy", "Light drizzle", "Thunderstorm" and so on) are mapped from the standard World Meteorological Organization (WMO) weather codes returned by the forecast model.

Air quality (AQI)

Air-quality figures on our Indian city pages come from the Open-Meteo Air Quality API, which uses forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). CAMS provides modelled PM2.5 and PM10 concentrations; it doesn't publish India's AQI directly.

We estimate the AQI on India's national scale (CPCB National Air Quality Index) from the 24-hour average of PM2.5 and PM10, using CPCB's official breakpoints, and show the higher of the two sub-indices. Because this is based on a model covering a wide grid area and only two pollutants, it can differ from readings at a specific CPCB monitoring station. For official values, see CPCB's AQI portal.

How fresh is the data?

Data is requested live from your browser each time you load a page or search a place — we don't cache or store forecasts on our servers. The underlying models are updated by their providers several times a day.

Limits of forecast data

Model forecasts are estimates, not guarantees. They are usually most reliable for the next 1–3 days and less certain further out. Local effects — hills, coastlines, cities — can make conditions at your exact spot differ. For official warnings, always rely on your national weather service. Read more in our Disclaimer.

Attribution

Weather data by Open-Meteo.com, licensed under CC BY 4.0. Air-quality data generated using Copernicus Atmosphere Monitoring Service information.