You can see the weather data format by
- make sure you installed the webCoRE storage app (it gathers and updates the $weather variable)
- setup the webcore main app to enable weather and your source and key, and done your way out.
- Go to the webcore storage app (HE console -> apps -> select the webcore storage app) and click on "dump weather structure" - this will let you see what you have to work with based on your source
- In your piston, that is accessed via $weather... (of what you see in the dump).
The different sources for weather have different data, formats/spelling of variables, so hence you need to see the dump.
There are many example weather pistons in the webCoRE forum (most of these are for $twc as a source which ST uses (which is a paid service, so not on HE), but these examples can help you start with something and then adjust the data reference).
The storage app does attempt to add icon references to the weather data as well as a $weather.weatherType variable to give you the source setting into the piston.
I just added OpenWeather, but I have not adjusted my pistons to that format yet.
Another note - many times weather data has times embedded as integer numbers (these could be seconds since epoch, or milliseconds since epoch). HE webcore can make these time or datetime directly (ie dateTime(value)) vs. all the gyrations you may see in ST pistons to fix time as numbers...
