Nuageux vs. couvert
The French words 'nuageux' and 'couvert' are meteorological terms commonly used to describe different types of cloudy skies, each with subtleties in meaning that affect their usage.
Nuageux
This term is used to describe weather characterized by the frequent presence of clouds in the sky, but not necessarily indicating a completely filled sky.
Le ciel est nuageux aujourd'hui, mais le soleil brille par moment.
(The sky is cloudy today, but the sun shines through at times.)
Il fait nuageux ce matin, parfait pour une promenade sans trop de soleil.
(It's cloudy this morning, perfect for a walk without too much sun.)
Un temps nuageux est prévu pour l'après-midi avant la pluie ce soir.
(Cloudy weather is forecasted for the afternoon before rain tonight.)
Couvert
'Couvert' specifically refers to an overcast sky where clouds completely cover the sky, resulting often in a gray and uniform appearance without clear breaks.
Le ciel est couvert, il va probablement pleuvoir.
(The sky is overcast; it is probably going to rain.)
Avec un ciel couvert comme aujourd'hui, il est difficile de déterminer l'heure qu'il est.
(With an overcast sky like today, it is hard to tell the time.)
Lorsque le temps est couvert en hiver, les températures peuvent rester très basses toute la journée.
(When the weather is overcast in winter, temperatures can stay very low all day long.)
Summary
'Nuageux' generally refers to a sky with many clouds, but with occasional breaks that could allow sunlight to pass through. In contrast, 'couvert' refers to a completely overcast sky with no breaks in the cloud cover. The word 'nuageux' conveys a sense of variability and patchiness, whereas 'couvert' conveys density and uniformity.