Could you let me know the difference between these two adjectives? In my book they seem to be slightly different(by it's not clearly explained) while on the internet most people say that they've the same meaning, just 'muggy' is more colloquial. Could you enlighten me?
muggy is an informal term that refers to the discomfort of humidity. Synonyms would be stifling, airless, oppressive, sticky, clammy.
humid is, or at least can be, a neutral term that refers to moisture in the air.
For example, the air in the Pacific Northwest is quite humid, but people who live there do not feel it to be muggy.
According to this website:
As adjectives the difference between humid and muggy. is that humid is containing sensible moisture (usually describing air or atmosphere); damp; moist; somewhat wet or watery; as, humid earth; consisting of water or vapor while muggy is humid, or hot and humid.
"Muggy" has a connotation of hot, still air, while "humid" doesn't.
For example, if the humidity is high but there's a strong breeze, it's humid, but you wouldn't call it muggy.
Or for a better example, sometimes in the fall, the air is really still and saturated, and it's too cool to go out in short sleeves, but with a jacket or heavy shirt, you feel sticky and gross because the air is so moist that it's like having a film of water all over you. That's humid, but it isn't muggy.