Learn Spanish (Latin America): No vamos a pasear hoy porque hace mucho calor. - We are not going to take a walk today because it is very hot.

The near future is formed with a conjugated form of ir (to go), the word a, and an action verb in its basic, unchanged form (an infinitive). Here, we have vamos a pasear (we are going to take a walk). To make it negative, you simply put no right in front of the conjugated verb vamos.

Why do we use hace instead of a word for "is" (like es or está) to say "it is hot"?

In English we say the weather is a certain way, but in Spanish, common weather expressions use the verb hacer (to make or do). You are literally saying "it makes heat". You cannot use es or está with calor.

The translation says "very hot", so why does the Spanish say mucho (a lot) instead of muy (very)?

In Spanish, calor is a noun meaning "heat", not an adjective meaning "hot". Because it is a noun, you must describe it with mucho (a lot of) rather than muy (very). The literal translation of hace mucho calor is "it makes a lot of heat."

What is the difference between pasear and caminar?