This mod can be incompatible with other mods that change the weather system.
Backup your gamedata folder just in case and install on your own responsibility.

1. In case you haven't installed any mods before, locate file "fsgame.ltx" in the main S.T.A.L.K.E.R. directory, open with
   Notepad and change both variables in this line to "true": $game_data$ = true | true | $fs_root$ | gamedata\
2. Run AtmosFear Setup and follow the instructions.
3. Start the game. Load last save or start new game (starting a new game is not required)
4. Open game console (default key is '`')
5. Save backup of your settings by entering: cfg_save user_bak
6. Load desired AtmosFear settings by entering: cfg_load user_atmosfear_desired_settings (e.g. cfg_load user_atmosfear).
   NOTE: This step will overwrite some your graphic settings. Settings like key bindings, resolution and most of the advanced graphic options will stay the same. Gamma/contrast/brightness settings will be set to 1/1.3/1.2 but you can adjust it to your personal taste.

1. Go to Start Menu > Programs > Cromm Cruac
2. Run Uninstall AtmosFear CS v1.3
3. Start the game. Load last save or start new game.
4. Open game console (default key is '`')
5. Load the back-up of your settings by entering: cfg_load user_bak.ltx
6. Restart the game.

This mod can seriosly stress your graphic card as it is designed for high-end graphic cards. However, it has been tested on double SLi-ed 8800GTS with lowered graphic settings with pretty decent results in framerate.

If you experience drop in framerate try to reduce Object details, SSAO, Sun rays quality settings in advanced graphics settings and/or resolution in basic settings.

Don't change in-game basic preset (low, medium, high).

The mod has been designed and tested on version 1.5.10 but should work on other CS versions.