A phenomenon encountered while smoking (usually weed). Someone takes an average sized hit from the smoking apparatus, and upon exhaling, the smoker blows out a huge cloud of smoke from what was a seemingly huge, lung-busting rip. In reality, the hit wasn't that big, as it was augmented by the condensation from the cold winter air, hence the name, "winter hit," or "frost hit"
smoker 1: "*exhales* dude, look at all that smoke! that was crucial hit i just took."
smoker 2: "*sighs* just another frost hit"