Oggi il cielo è nuvoloso.

In Italian you almost always use a definite article with singular, countable nouns—even in general statements. il cielo (“the sky”) is required here.
– Saying Oggi cielo è nuvoloso sounds ungrammatical in everyday speech.
– In very terse weather bulletins you may hear just Nuvoloso or Oggi nuvoloso, but that’s a special, elliptical style.

The grave accent on è marks the third-person singular present of essere (“to be”), distinguishing it from the conjunction e (“and”).
– è = “he/she/it is”
– e = “and”
Omitting the accent would cause confusion with e, so it’s mandatory.

nuvoloso is an adjective derived from nuvola (“cloud”) + -oso (a suffix meaning “full of”). It agrees in gender and number with the noun it modifies:
– masculine singular: nuvoloso
– masculine plural: nuvolosi
– feminine singular: nuvolosa
– feminine plural: nuvolose

Both mean “cloudy,” but with a nuance:
– nuvoloso = there are visible clouds; the sky is partly to mostly cloudy.
– coperto = completely overcast; no clear patches at all.

Italian word order is fairly flexible. Placing Oggi at the front emphasizes the time:
– Oggi il cielo è nuvoloso (Today, the sky is cloudy.)
– Il cielo è nuvoloso oggi (The sky is cloudy today.)
Both are correct; choose based on what you want to stress.

In Italian, when describing the sky or general weather with an adjective, you use essere:
– Il cielo è nuvoloso
– Il tempo è bello
To talk about temperature you use fare:
– Fa freddo (It’s cold)
– Fa caldo (It’s hot)

Pronunciation: nu-vo-LO-so
– Four syllables: nu-vo-lo-so
– Stress on the third syllable: LO
IPA phonetic: [nuvoˈlɔːso] (the o in “lo” is open, similar to the vowel in English “law”).