It's a fair question. There's a lot of free sources of data out there. This app is powered by our own Weather API: https://www.xweather.com/weather-api
The data is aggregated from global meteorological offices and other sources (some free, some paid). Some of the datasets are proprietary to us. For example, the lightning layers come from our own lightning detection network, and certain forecasts (like hail) are developed in-house.
This app was built to showcase our data. The vector mapping tools are also available via API. https://www.xweather.com/mapsgl
This is true for many free weather APIs out there. But our weather API is global so we’re not just passing through a single government feed. There’s quite a bit of engineering to normalize all of the data sources. Japanese alerts for example are just XML feeds. All the sources update on different schedules, and have different forecast ranges, so it's a challenge to make sure the best forecast is returned at request time.
Some of our data is proprietary. The lightning strike data is from our own lighting detection network. We also offer the only hail forecast model available which was developed in house :)
Did you manage to track down their other services’ providers and negotiate access?