Does うららか mean "beautiful" (as in "beautiful weather") in the sentence below?
うららかな午後に、新木場で起きた事故で電車ビタ止まり。
Written by a Japanese colleague on our discussion server.
Google Image Search does not show nice weather in particular when searching for うららか or うららかな午後.
"Beautiful" is surely included in the meaning of 「うららか」, but its more important base meaning is "spring-like" ("printanier" in your language). In the world of haiku, 「うららか」 simply means "spring" itself.
A very beautiful day in any other seasons would usually not be described as 「うららか」by native speakers regardless of how beautiful the day is. It just feels wrong to do so.
It is such an elegant word that it is difficult to translate except for saying that it is along the lines of "peaceful, beautiful, refreshing and spring-like".