Learn Spanish (Latin America): Tenemos calor en la casa.

In Spanish, physical states like feeling hot, cold, hungry, or thirsty are expressed using the verb tener (to have) followed by a noun. So instead of saying "we are hot," you are literally saying "we have heat" (Tenemos calor).

Can I just say estamos calientes to mean "we are hot"?

You definitely want to avoid that! When talking about people, using the verb estar (to be) with the adjective caliente (hot) usually means sexually aroused. Always use tener calor to say a person is feeling hot.

Where is the word for "we" in this sentence?

The verb ending in tenemos already tells us the subject is "we." Because of this, the pronoun nosotros (we) is optional and is usually left out in everyday Spanish.

Could I say en casa instead of en la casa?

Yes, but the meaning changes slightly. En casa translates to "at home," while en la casa means "in the house." This sentence emphasizes the physical building where it is hot.