I would say "the sun can only be shining" instead of "the sun can only shine", but English is not my native language and I may very well be wrong.

In specifications, "there may be no clouds" is ambiguous. Unambiguous would be "there must be no clouds".

Use appropriate datatypes. Temperature should be an Int, not a String. If this kata is to be about "parsing" ( quite a grandiose term for what is actually needed ), focus on that. Do one thing, and do it well.