Program: 81892
Project: 81892
Buggy source:
public void tickParticlePrecipitation(){
  if (ConfigParticle.Particle_RainSnow) {
    EntityPlayer entP=FMLClientHandler.instance().getClient().thePlayer;
    if (entP.posY >= StormObject.static_YPos_layer0)     return;
    float curPrecipVal=getRainStrengthAndControlVisuals(entP);
    float maxPrecip=0.5F;
    int precipitationHeight=entP.worldObj.getPrecipitationHeight(new BlockPos(MathHelper.floor_double(entP.posX),0,MathHelper.floor_double(entP.posZ))).getY();
    Biome biomegenbase=entP.worldObj.getBiomeGenForCoords(new BlockPos(MathHelper.floor_double(entP.posX),0,MathHelper.floor_double(entP.posZ)));
    if (biomegenbase != null) {
      float temperature=biomegenbase.getFloatTemperature(new BlockPos(MathHelper.floor_double(entP.posX),MathHelper.floor_double(entP.posY),MathHelper.floor_double(entP.posZ)));
      double d3;
      float f10;
      curPrecipVal=Math.min(maxPrecip,Math.abs(curPrecipVal));
      World world=entP.worldObj;
      Random rand=entP.worldObj.rand;
      if (curPrecipVal > 0) {
        if (entP.worldObj.getBiomeProvider().getTemperatureAtHeight(temperature,precipitationHeight) >= 0.15F) {
          int spawnAreaSize=15;
          for (int i=0; i < curPrecipVal * 20F * ConfigParticle.Precipitation_Particle_effect_rate; i++) {
            BlockPos pos=new BlockPos(entP.posX + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2),entP.posY - 5 + rand.nextInt(15),entP.posZ + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2));
            if (world.isRainingAt(pos)) {
              ParticleTexExtraRender rain=new ParticleTexExtraRender(entP.worldObj,pos.getX(),pos.getY(),pos.getZ(),0D,0D,0D,ParticleRegistry.rain);
              rain.setCanCollide(true);
              rain.setKillOnCollide(true);
              rain.windWeight=1F;
              rain.setFacePlayer(false);
              rain.rotationYaw=rain.getWorld().rand.nextInt(360) - 180F;
              rain.setMotionY(-0.5D);
              rain.spawnAsWeatherEffect();
              ClientTickHandler.weatherManager.addWeatheredParticle(rain);
            }
          }
        }
 else {
          int spawnAreaSize=50;
          for (int i=0; i < curPrecipVal * 20F * ConfigParticle.Precipitation_Particle_effect_rate; i++) {
            BlockPos pos=new BlockPos(entP.posX + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2),entP.posY - 5 + rand.nextInt(15),entP.posZ + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2));
            if (canPrecipitateAt(world,pos)) {
              ParticleTexExtraRender snow=new ParticleTexExtraRender(entP.worldObj,pos.getX(),pos.getY(),pos.getZ(),0D,0D,0D,ParticleRegistry.snow);
              snow.setMotionY(-0.3D);
              snow.setScale(1.3F);
              snow.setGravity(0.1F);
              snow.windWeight=0.2F;
              snow.setMaxAge(200);
              snow.setFacePlayer(false);
              snow.setCanCollide(true);
              snow.setKillOnCollide(true);
              snow.rotationYaw=snow.getWorld().rand.nextInt(360) - 180F;
              snow.spawnAsWeatherEffect();
              ClientTickHandler.weatherManager.addWeatheredParticle(snow);
            }
          }
        }
      }
    }
  }
}

Fixed version (ground truth):
public void tickParticlePrecipitation(){
  if (ConfigParticle.Particle_RainSnow) {
    EntityPlayer entP=FMLClientHandler.instance().getClient().thePlayer;
    if (entP.posY >= StormObject.static_YPos_layer0)     return;
    WeatherManagerClient weatherMan=ClientTickHandler.weatherManager;
    if (weatherMan == null)     return;
    WindManager windMan=weatherMan.getWindManager();
    if (windMan == null)     return;
    float curPrecipVal=getRainStrengthAndControlVisuals(entP);
    float maxPrecip=0.5F;
    int precipitationHeight=entP.worldObj.getPrecipitationHeight(new BlockPos(MathHelper.floor_double(entP.posX),0,MathHelper.floor_double(entP.posZ))).getY();
    Biome biomegenbase=entP.worldObj.getBiomeGenForCoords(new BlockPos(MathHelper.floor_double(entP.posX),0,MathHelper.floor_double(entP.posZ)));
    if (biomegenbase != null) {
      float temperature=biomegenbase.getFloatTemperature(new BlockPos(MathHelper.floor_double(entP.posX),MathHelper.floor_double(entP.posY),MathHelper.floor_double(entP.posZ)));
      double d3;
      float f10;
      curPrecipVal=Math.min(maxPrecip,Math.abs(curPrecipVal));
      World world=entP.worldObj;
      Random rand=entP.worldObj.rand;
      if (curPrecipVal > 0) {
        if (entP.worldObj.getBiomeProvider().getTemperatureAtHeight(temperature,precipitationHeight) >= 0.15F) {
          int spawnAreaSize=15;
          for (int i=0; i < curPrecipVal * 20F * ConfigParticle.Precipitation_Particle_effect_rate; i++) {
            BlockPos pos=new BlockPos(entP.posX + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2),entP.posY - 5 + rand.nextInt(15),entP.posZ + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2));
            if (world.isRainingAt(pos)) {
              ParticleTexExtraRender rain=new ParticleTexExtraRender(entP.worldObj,pos.getX(),pos.getY(),pos.getZ(),0D,0D,0D,ParticleRegistry.rain);
              rain.setCanCollide(true);
              rain.setKillOnCollide(true);
              rain.windWeight=1F;
              rain.setFacePlayer(false);
              rain.rotationYaw=rain.getWorld().rand.nextInt(360) - 180F;
              rain.setMotionY(-0.5D);
              rain.spawnAsWeatherEffect();
              ClientTickHandler.weatherManager.addWeatheredParticle(rain);
            }
          }
        }
 else {
          int spawnAreaSize=50;
          for (int i=0; i < curPrecipVal * 20F * ConfigParticle.Precipitation_Particle_effect_rate; i++) {
            BlockPos pos=new BlockPos(entP.posX + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2),entP.posY - 5 + rand.nextInt(15),entP.posZ + rand.nextInt(spawnAreaSize) - (spawnAreaSize / 2));
            if (canPrecipitateAt(world,pos)) {
              ParticleTexExtraRender snow=new ParticleTexExtraRender(entP.worldObj,pos.getX(),pos.getY(),pos.getZ(),0D,0D,0D,ParticleRegistry.snow);
              snow.setMotionY(-0.3D);
              snow.setScale(1.3F);
              snow.setGravity(0.1F);
              snow.windWeight=0.2F;
              snow.setMaxAge(200);
              snow.setFacePlayer(false);
              snow.setTicksFadeInMax(10);
              snow.setAlphaF(0);
              snow.setCanCollide(true);
              snow.setKillOnCollide(true);
              snow.rotationYaw=snow.getWorld().rand.nextInt(360) - 180F;
              snow.spawnAsWeatherEffect();
              ClientTickHandler.weatherManager.addWeatheredParticle(snow);
            }
          }
        }
      }
    }
  }
}