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Mausam Online

How we predict the weather

Mausam Online is built on open, professional-grade weather data. Every temperature, rainfall, wind, and air-quality number you see on the site comes from one of two world-class sources, served through the open-data project Open-Meteo. There is no in-house forecasting model and no AI guess — we surface raw outputs from the same systems that national met departments and airlines rely on.

Weather forecast: ECMWF + GFS via Open-Meteo

Our hourly and 7-day forecasts come from two of the world's leading numerical weather prediction (NWP) models:

Both models are blended and served by Open-Meteo, a non-profit Swiss project that aggregates and re-distributes open weather data. We refresh each city's reading every 60 minutes.

Air quality: European AQI

Our AQI badges use the official European Air Quality Index (EAQI) defined by the European Environment Agency. The scale runs 0–100+ with breakpoints at 20/40/60/80/100, and combines PM2.5, PM10, NO₂, O₃ and SO₂ readings into a single number.

Source: Copernicus Atmosphere Monitoring Service (CAMS) global air-quality forecast, served via Open-Meteo's Air Quality API.

Why EAQI instead of the US or Indian AQI?

South Asia uses several competing AQI scales (Indian NAQI 0–500, US EPA 0–500, EAQI 0–100+). We chose EAQI because (1) it weights PM2.5 and PM10 separately so dust storms and combustion smog produce clearly different scores, (2) it has documented sub-pollutant breakpoints that we can publish for every reading, and (3) it is the scale Open-Meteo natively exposes. We don't translate to NAQI / US AQI to avoid silent rounding errors — instead we always show the underlying PM2.5 / PM10 µg/m³ values on the city page.

How accurate are the forecasts?

For the first 24 hours, ECMWF-blended forecasts are routinely within ±1.5°C of observed temperature in South Asia. For days 4–7, accuracy drops as expected with any global model — typical error grows to ±3–4°C and rainfall timing within ±6 hours. We do not over-promise: a 7-day forecast is guidance, not a guarantee.

Update cadence — what refreshes when

What we don't do

Open data, open code

Mausam Online's static-site code is open source and the data sources above are all public APIs. If you want to verify a number, point any HTTP client at the same Open-Meteo endpoint and you'll get the same JSON we did.

Why we exist

Most weather apps for South Asia are either bloated international products (slow on low-end Android, no Tamil/Bengali/Urdu UI) or thin scrapers that mirror the same data without context. We try to be neither: fast (under 0.8s LCP on 3G), localised (5 languages with native-script city names), and honest about where the numbers come from.

Who runs Mausam Online

Mausam Online is built and operated by Spolek Minizoo.cz z.s., a Czech-Republic-registered nonprofit association (IČO listed on the parent site at minizoo.cz). The organisation also operates sister weather sites for Central Europe (pocasi.online — Czech), the Balkans (vrijeme.online), and the DACH region (vorhersage.online).

Operational responsibility for forecast quality, AQI methodology, and city/state geo-data sits with the engineering team. Data anomalies, accuracy disputes and methodology questions can be raised via the contact page — we aim to respond within 5 working days.

This page was last reviewed on and is updated whenever a methodology change ships (e.g. switching AQI provider, adding a new model, or revising onset heuristics).