There are various ways to discuss the weather. You start with either: Hace, Hay, or Está. These cannot be switched around at will, but follow specific patterns and rules.
Hace sol. = It is sunny.
Hace calor. = It is hot.
Hace frío. = It is cold.
Hace fresco. = It is cool.
Hace viento. = It is windy.
Hace buen tiempo. = It is nice out/It is nice weather.
Hace mal tiempo. = it is bad out/It is bad weather.
Hace tormenta. = It is stormy (not in book)
Hace niebla. = It is foggy. (not in book)
Hay sol. = There is sun.
Hay viento. = There is wind.
Está nublado. = It is cloudy
Está lloviendo. = It is raining. (not in book)
Está nevando. = It is snowing. (not in book)
You would use these last two if it is actually raining or snowing when you say the sentence.
¿Qué tiempo hace?
Está lloviendo ahora. = It is raining now.
Llover = To rain
Nevar = To snow
You would use these verbs when you are talking about the weather in general terms:
eg. En el invierno, nieva mucho. = In the winter, it snows a lot.
En la primavera, llueve mucho. = In the spring, it rains a lot.
These expressions are used to talk about feelings you have. They use the verb "tener", which means "to have", but the sentence in English is translated using the verb "to be". You conjugate the verb "tener" and add the feeling:
Eg Yo tengo frío. = I am cold (you feel cold)
Don't confuse this with "Hace frío", which means "It is cold". (weather is cold)