"What's the weather like?" in French?	"Quel temps fait-il?" Le temps means weather (and time).
"It's hot" and "it's cold" in French?	"Il fait chaud." "Il fait froid." Most weather phrases use faire.
"The weather is nice" and "the weather is bad" in French?	"Il fait beau." "Il fait mauvais."
"It's sunny" and "it's windy" in French?	"Il y a du soleil." "Il y a du vent."
"It's raining" and "the rain" in French?	"Il pleut." La pluie.
"It's snowing" and "the snow" in French?	"Il neige." La neige.
"It's cloudy" and "the cloud" in French?	"Le ciel est nuageux" or "il y a des nuages." Le nuage. Also "il fait gris."
"The thunderstorm", "thunder" and "lightning" in French?	L'orage (m.). Le tonnerre (thunder). L'éclair (m., lightning). A windstorm is une tempête.
"Fog" in French?	Le brouillard. "Il y a du brouillard" (it's foggy).
"It's twenty degrees" in French?	"Il fait vingt degrés." La température = the temperature.
"I'm cold" vs "it's cold" in French?	"J'ai froid" (I feel cold) vs "il fait froid" (the weather is cold). "Je suis froid" describes a cold personality.
"The four seasons" in French?	Le printemps (spring), l'été (summer), l'automne (autumn), l'hiver (winter). All four are masculine.
"In spring" and "in summer" in French?	Au printemps, but en été. The other seasons also take en: en automne, en hiver.
"The sun", "the moon" and "the sky" in French?	Le soleil, la lune, le ciel.
"The tree" and "the flower" in French?	L'arbre (m.), la fleur.
"The mountain" and "the river" in French?	La montagne. Le fleuve (flows into the sea) or la rivière (flows into another river or lake).
"The sea" and "the beach" in French?	La mer, la plage. La mer sounds the same as la mère (mother) and le maire (mayor).
"The lake" and "the forest" in French?	Le lac, la forêt.
"The countryside" in French?	La campagne. "J'habite à la campagne" (I live in the countryside).
"The island" and "the desert" in French?	L'île (f.), le désert. Don't confuse it with le dessert (pudding), spelled with ss.
"The earth" and "the world" in French?	La terre (soil, land; la Terre is planet Earth). Le monde. Tout le monde means everyone.
"The bird" and "the animal" in French?	L'oiseau (m., plural oiseaux), l'animal (m., plural animaux).
"The rainbow" in French?	L'arc-en-ciel (m.). Plural: des arcs-en-ciel.
"The environment" in French?	L'environnement (m.). "Il faut protéger l'environnement."
"Climate change" in French?	Le changement climatique (also le dérèglement climatique).