Hello,
This is the Lite-C weather script you needed, translated from George's C-Script weather code :

#include <acknex.h>
#include <default.c>

#define CONTENT_SOLID 3

/////////////////////////////////////////////////////////////////////////////////////////////

var rain_on = 0;
var snow_on = 0;
var fog1_on = 0;
var fog2_on = 0;
var fog3_on = 0;
var fog4_on = 0;

var rain_handle; // handle for the rain.wav sound
var snow_handle; // handle for the snow.wav sound

var day = 0;

/////////////////////////////////////////////////////////////////////////////////////////////

BMAP *snow_tga = "snow.tga";

/////////////////////////////////////////////////////////////////////////////////////////////

STRING *work40_wmb = "work40.wmb";

STRING *rain_tga = "rain.tga";

/////////////////////////////////////////////////////////////////////////////////////////////

SOUND *rain_wav = "rain.wav";
SOUND *snow_wav = "snow.wav";

/////////////////////////////////////////////////////////////////////////////////////////////

function fade_snow(PARTICLE *p);
function snow_particles(PARTICLE *p);
function toggle_snow();
function snow_sound();

function rain_sprites();
function toggle_rain();
function rain_sound();

function toggle_fog();

function toggle_daynight();

/////////////////////////////////////////////////////////////////////////////////////////////

function main()
{
video_mode = 7; // 800x600 pixels
video_depth = 32; // 32 bit mode
video_screen = 1; // start in full screen mode
d3d_lightres = 128;

fps_max = 60;
max_entities = 30000;

level_load (work40_wmb);

on_s = toggle_snow;
on_r = toggle_rain;
on_f = toggle_fog;
on_d = toggle_daynight;
}

action players_code () // simple player and 1st person camera code
{
player = my; // I'm the player
set( my, INVISIBLE ) ; // no need to see player's model in 1st person mode
while (1)
{
// move the player using the "W", "S", "A" and "D" keys; "10" = movement speed, "6" = strafing speed
c_move (my, vector(6 * (key_cuu - key_cud) * time_step, 4 * (key_cul - key_cur) * time_step, 0), nullvector, IGNORE_PASSABLE | GLIDE);
vec_set (camera.x, player.x); // use player's x and y for the camera as well
camera.z += 30; // place the camera 30 quants above the player on the z axis (approximate eye level)
camera.pan -= 5 * mouse_force.x * time_step; // rotate the camera around by moving the mouse
camera.tilt += 3 * mouse_force.y * time_step; // on its x and y axis
player.pan = camera.pan; // the camera and the player have the same pan angle
wait (1);
}
}

/////////////////////////////////////////////////////////////////////////////////////////////

function toggle_snow()
{
snow_on += 1;
snow_on %= 2;
VECTOR snow_origin;
var i;
while (!player) {wait (1);}
snow_sound();
while (snow_on)
{
i = 0;
while (i < 50) // that's a "while without wait" loop
{
snow_origin.x = player.x + 1000 - random(2000);
snow_origin.y = player.y + 1000 - random(2000);
snow_origin.z = player.z + 300;
effect(snow_particles, 1, &snow_origin, normal);
i += 1;
}
if(random(1) > 0.7)
{
c_move (player, nullvector, vector((-1 + random(1)) * time_step, 0, 0), IGNORE_PASSABLE | GLIDE);
}
wait (1);
}
}

function snow_particles(PARTICLE *p)
{
VECTOR particle_direction;
particle_direction.x = random(5) - 15;
particle_direction.y = (1 - random(2)) / 10;
particle_direction.z = -5 - random(7);

vec_add(p.vel_x, &particle_direction);
p.alpha = 30 + random(65);
p.bmap = snow_tga;
p.size = 3;
set(p,BRIGHT | MOVE) ;
p.event = fade_snow;
}

function fade_snow(PARTICLE *p)
{
p.alpha -= 1.2 * time_step;
if (p.alpha < 0) {p.lifespan = 0;}
}

function snow_sound()
{
if (snow_on)
{
snow_handle = snd_loop(snow_wav, 50, 0);
}
else
{
snd_stop(snow_handle);
}
}

/////////////////////////////////////////////////////////////////////////////////////////////

function toggle_rain()
{
rain_on += 1;
rain_on %= 2;
VECTOR rain_origin;
var i;
while (!player) {wait (1);}
rain_sound();
while (rain_on)
{
i = 0;
while (i < 30) // that's a "while without wait" loop
{
rain_origin.x = player.x + 500 - random(1000);
rain_origin.y = player.y + 500 - random(1000);
rain_origin.z = player.z + 300;
ent_create(rain_tga, &rain_origin, rain_sprites);
i += 1;
}
rain_origin.x = player.x + 100 - random(200);
rain_origin.y = player.y + 100 - random(200);
rain_origin.z = player.z + 500;
ent_create(rain_tga, &rain_origin, rain_sprites);
wait (1);
}
}

function rain_sprites()
{
set ( my, PASSABLE | TRANSLUCENT | BRIGHT /*| UNLIT*/ ) ; // remove the comment to increase the brightness of the rain sprites
my.alpha = 20 + random(75);
my.ambient = 40 + random(60);

while (my.alpha > 0)
{
if (c_content(my.x, 0) == CONTENT_SOLID)
{
my.alpha = 0;
}
my.z -= (25 + random(30)) * time_step;
wait (1);
}
ent_remove(my);
}

function rain_sound()
{
if (rain_on)
{
rain_handle = snd_loop(rain_wav, 50, 0);
}
else
{
snd_stop(rain_handle);
}
}

/////////////////////////////////////////////////////////////////////////////////////////////

function toggle_fog()
{
fog1_on += 1;
fog1_on %= 2;
if (fog1_on)
{
camera.fog_start = 10;
d3d_fogcolor1.red = 55;
d3d_fogcolor1.green = 55;
d3d_fogcolor1.blue = 55;
fog_color = 1;
while (fog1_on)
{
camera.fog_end = 1000 + 400 * sin(0.05 * total_frames * time_step);
wait (1);
}
}
else
{
fog_color = 0;
}
}

/////////////////////////////////////////////////////////////////////////////////////////////

ENTITY *fading_ent =
{
type = "fader.mdl";
layer = 10;
alpha = 0;
pan = 90;
flags = TRANSLUCENT | SHOW;
view = camera;
x = 250; // 250 quants ahead of the view
y = 0;
z = 0;
}

function toggle_daynight()
{
day += 1;
day %= 2;
if (day)
{
while (day)
{
camera.ambient = minv(100, camera.ambient + 1 * time_step);
fading_ent.alpha = maxv(0, fading_ent.alpha - 1 * time_step);
wait (1);
}
}
else // night
{
while (!day)
{
camera.ambient = maxv(-100, camera.ambient - 1 * time_step);
fading_ent.alpha = minv(70, fading_ent.alpha + 1 * time_step);
wait (1);
}
}
}

/////////////////////////////////////////////////////////////////////////////////////////////


Regards.