In English, we have different grammatical structures to describe the weather, using verbs, adjectives, and the like. In French, they also have different patterns that you will find. There are two main structures. Both are formed using the subject "il" (it). The first uses the verb "faire" (to do), which conjugates as "fait" for the subject "il." Here are some of the more common phrases:
Il fait beau - The weather's nice
Il fait chaud - It's hot
Il fait froid - It's cold
Il fait frais - It's cool
Il fait mal - The weather's bad
Il fait du vent - It's windy
The other way to talk about the weather is with a specific verb, such as to rain or to snow. Here are some examples:
Il pleut - It's raining
Il neige - It's snowing
Il gèle - It's freezing
You can of course use these in combinations as well. For example, you might say "Il fait mail, parce qu'il pleut beaucoup" to say that the weather's bad because it's raining a lot. If you want to ask what the weather is like, you use the question "Que temps fait-il?" You can see the "il fait" structure in this question as well, though it is inverted, making it a question. The word "temps" (masc.) is the general word for weather.