stifling

1. Very hot or stuffy almost to the point of being suffocating.
2. Being of such a character or nature as to engender a feeling of stultification, repression, or suffocation: "The scholarly correctness of our age can be stifling" (Annalyn Swan).

adjective

Oppressive due to a lack of fresh air: airless, close, stuffy. See breath/breathlessness, open/close.

Definition: very hot
Antonyms: chilly, cold

The noun has one meaning:

Meaning #1: forceful prevention; putting down by power or authority
  Synonyms: suppression, crushing, quelling

The adjective stifling has one meaning:

Meaning #1: characterized by oppressive heat and humidity
  Synonyms: sultry, sulfurous, sulphurous