FCC Weather API - question

Dear Friends,

Do I understand correctly that this FCC Weather API is not stable yet and can be changed anytime? I have a trouble with weather icons. Yesterday I could access it with weather[0].icon and there was only one element in the array, but today it looks that there are already two elements and the icon-key value is not a path to the icon file anymore.

"weather":[{"id":521,"main":"Rain","description":"shower rain"},{"id":211,"main":"Thunderstorm","description":"thunderstorm","icon":"11d"}]


"weather":[ { "id":500, "main":"Rain", "description":"light rain", "icon":"https://cdn.glitch.com/6e8889e5-7a72-48f0-a061-863548450de5%2F10n.png?1499366021399" } ]

Any ideas?