this mod was created by CAPA here is link to original I just updated it to nextgen version and make sure it doesn't modify any vanilla game scripts and ported this over to modBootstrap

be-aware to use this mod you need modBootstrap-v.0.4.1-NEXT-GEN without it this will not work and read the instructions below and install it properly before reporting any error

Note:
if you choose to disable the effect in cutscenes or dialogues(via the menu) the effect will stop 5 to 10  seconds into the dialogue or cutscene(sorry I can't fix this properly because this mod is hacky and there are some limitations). and about dead bodies playing the effect I'm clueless on how to fix it but I'm working on it

What it does?

Enables Ice Breath FX to Geralt, Roach and NPCs( Men, Women, Children) while in Skellige.
Also as optional you can have Custom Snow particles to some Skellige Weathers.

How it works?

Now with v2 you have some options using the menu!
MENU > OPTIONS > MODS > ICE BREATH SETTINGS

Cold Places: Enables the effect to whatever weather when you are at: 

• AN_Skellige_ArdSkellig
• AN_Island_of_Myst
• AN_Prologue_Village_Winter
• AN_Kaer_Morhen
  

(If you don't set anything to the menu or choose to not have it, "Cold Places" will be the default behaviour)

Cold Weather: Enables the effect based on the current Weather does not matter the Map you are.

Compatibility: when using the cold weather options the FX will be only Enabled during foggy, snowy and cold weathers. the mod is now officially compatible with these mods (thanks to ElementaryLewis for helping with these):

• Immersive Lighting
• Skellige Winter Weather System
• Realistic Weather
• also compatible with Vanilla Game(NGE) without any lighting mods
• More Variable Weather,  Grim Lighting, Benis Lighting and Better Vanilla Lighting
  

Note: I'll do no further patches with any other lighting mods in future I'll leave it to other modders


Forced: It will enable the effect no matter what

Disabled: Will never enable the effect

The script checks the conditions of area, weather and settings from 5 to 5 seconds.(no hotkeys needed)
So when you choose something from the menu it will have effect after 5 seconds.

Examples:

• To Skellige always on, choose "Cold Places"
• Don't want Skellige to always have it enabled. Choose Cold Weather or Disabled
• Didn't like Kaer Morhen with Breath Fx? Choose Cold Weather or Disabled.
• Want to have have Ice Breath to Rain Weather in Velen? Choose Forced
  

Installation:

• download modBootstrap (modBootstrap-v.0.4.1-NEXT-GEN) and (modBootstrap-registry) install it as it says on instruction
• download this mod and extract all the files in witcher 3 directory where the bin and dlc folder is located
• now go to mods\modBootstrap-registry\content\scripts\local and open mods_registry.ws and add following line: add(modCreate_CIceBreathMod()); under the line //add(modCreate_UiExampleMod()); here is in image showing how that look like: 
  
  
• now goto bin\config\r4game\user_config_matrix\pc and open dx11filelist.txt and dx12filelist.txt thenadd IceBreath.xml; at the end of the file like this: 
  
  
• you are done enjoy the game
  

Credits:
this mod was created by CAPA and converted to gameversion(v4.00) and modBootstrap by me. I uploaded this on nexus with his permission. and thanks to Aeltoth for introducing me to the vanilla functions for cutscene or dialogue checking.
compatibility:
if you want to update this mod for lighting mods(if they are compatible with nextgen version of the game) ask me in the comment section or open an issue on bugs section I'll try to update