Weather can be changed using setWeather and setWeatherBlended functions. In GTA: SA, every weather has different parameters for the sunrise, morning, midday, noon, afternoon, sunset, night and midnight, so a weather can vary a lot deppending of the time of the day.
Non-standard weather ID's between 20 and 255 are also supported, but they might be buggy at some moments of the day.
MTA: SA has custom weather functions which can modify how a weather is rendered, but in this list the weathers are described without taking that into account. Also, using setWeatherBlended allows for more undocumented effects.
For a complete weather gallery, containing images of every weather ID (0 to 255) shot at every in-game hour, visit this page.
Default GTA: SA weathers (registered in timecyc.dat)
Weather ID
Name from timecyc.dat
Screenshots at 12:00 PM
Description
0
EXTRASUNNY_LA
Applies a heat haze effect
In singleplayer, these are Los Santos specific weathers. They are clear weathers, with blue sky and few clouds.
1
SUNNY_LA
2
EXTRASUNNY_SMOG_LA
3
SUNNY_SMOG_LA
4
CLOUDY_LA
5
SUNNY_SF
In singleplayer, these are San Fierro specific weathers. They are more diverse than Los Santos': some of them are clear, but others are rainy or foggy.
6
EXTRASUNNY_SF
7
CLOUDY_SF
8
RAINY_SF
Starts a thunderstorm, with rain and lightnings
9
FOGGY_SF
Starts a cloudy, dense fog
10
SUNNY_VEGAS
In singleplayer, these are Las Venturas specific weathers. They are clear, dry weathers.
11
EXTRASUNNY_VEGAS
Applies scorching hot weather, with a heat haze effect
12
CLOUDY_VEGAS
13
EXTRASUNNY_COUNTRYSIDE
In singleplayer, these are Los Santos countryside specific weathers. They are dull, hazy, diverse weathers, with rainy ones.
14
SUNNY_COUNTRYSIDE
15
CLOUDY_COUNTRYSIDE
16
RAINY_COUNTRYSIDE
Starts a thunderstorm
17
EXTRASUNNY_DESERT
Apply a heat haze effect
In singleplayer, these are Bone County specific weathers. They are clear, dry, scorching hot weathers.
18
SUNNY_DESERT
Apply a heat haze effect
19
SANDSTORM_DESERT
Starts a dense sandstorm
20
UNDERWATER
In singleplayer, this is probably the weather used internally when camera is underwater. It is greenish and cloudy, so it appears to be a kind of contaminated weather.
21
EXTRACOLOURS_1
Adds a purple-ish color to the sky and objects
In singleplayer, these are weathers used in interiors. They are somewhat strange, dark weathers with gradiented skyline colors.
22
EXTRACOLOURS_2
Adds a black-white sky and a uniform light to objects
Other weather IDs
23 to 26: Pale orange weather.
27 to 29: Fresh blue weather.
30 to 32: Dark, cloudy, teal weather.
33: Dark, cloudy, brown weather.
34: Blue/purple, regular weather.
35: Dull brown weather.
36 to 38: Bright, foggy, orange weather.
39: Very bright weather. Night looks like day.
40 to 42: Blue/purple, cloudy weather.
43: Toxic, contaminated clouds weather.
44: Black/white sky weather, similar to 22.
45 to 60: Normal seeming weather with graphical bugs at evening.
100: Strange weather which makes objects disappear.
118: Stormy weather with pink sky and crystal water.
126 to 150: Horrible flashing red bugged weather.
151 to 175: Far draw distance weather with pink, purple and turquoise clouds.