As suggested by the game's title, expect to see dark, night time environments punctuated by rain, fog and cold. These effects are nicely done. The rain is absolutely miserable and makes you feel all wet. Fog rolls around eerily and I swear I could make out the form of demons and other hell-spawned beasties dancing to and fro. I breathed slowly with the stranger as frosty little clouds of breath left his lips.
Ambient sounds are great.
The wind was chilling and the patter of the rain was good. The environment came to life with the sound effects, which can but shouldn't be overshadowed by the graphics engine. Even the voice acting, which is notoriously cheesy in most computer games, is done fairly well. The musical score has the effect of setting up a great mood for the game. I found that the detail in Nocturne was great.