If you look at the TLF entries for jour and journée, you will see that both can mean the time during which there is light (“toute la journée“, “le jour et la nuit“). But only jour can mean both the daylight (like in “voir le jour = naître” and “lever du jour“, “coucher du jour“) and the 24-hour period.

It is true we say “C’est une belle journée” to mean that it is sunny. I think it is only more casual than “c’est un beau jour” which can be used in more formal situations: “c’est un beau jour pour se marier“, “c’est un beau jour pour mourir“.

The same difference exists between an/année (both year), matin/matinée (morning), soir/soirée (evening)

Intuitively speaking, “journée/année/…” refers to a span of time whereas “jour/an/…” is a unit of time. So we say “passer la journée à faire…”, “Toute la journée” (“spend the day doing…”, “the whole day”) but “passer le jour à faire…” and “tout le jour” are incorrect.
And we say “il y a trois jours” (“three days ago”) et “quel jour sommes nous ?” (“What day is it?”) but we don’t say “il y a trois journées” nor “quelle journée sommes nous”.

More details there https://www.lawlessfrench.com/vocabulary/an-jour-matin-soir-vs-annee-journee-matinee-soiree/