Hello, there!
I didn't post for too long, I guess.
Okay, we are going to do something very simple for this lesson.
Did you ever see snow in Singapore?
I guess you saw raining,
often, but I guess
you just saw artificial snows .
Today, we are going to control weather! YAY :D
OK, not funny.
Shall we start since you guys are not amazed by
my lame-shit? :/
Okay, as usual, please open your image by going to
File->Open / Double Click the background.

I opened this emo guy.
I kinda like his adidas shoes :/
Okay, whatever!
Now please new add layer and click the paint bucket tool. [:
I am sure everyone know how to add layer and click paint-bucket tool.
Okay, fill the new layer with black colour, please.


Now, please go to
Filter->Noise->Add Noise.

Please make sure that it is monochromatic [:
and GAUSSIAN!
Next, please go to Filter->Blur->Gaussian Blur.

Around 0.4~0.7 pixels (:
Then, go to Image->Adjustments->Threshold

Now adjust your own pixels.

Then you will see something like this:

Now, go to Filter->Blur->Motion Blur.

For Snow.

For Rain.

But this depends on your taste, as well!
Then you will see something like this:

Sorry for no captures this onwards.
Please go to Image->Adjustments->Bright/Contrast.
Adjust your own contrast&brightness , but please do lower the brightness and higher the contrast to show the white lines more.
Change the mode to Screen.
Then you will see the photo with rain/snow (:

Thanks. I know it's boring sials X:
But next lesson is changing ppl's face, like what TIMO suggested me [:
Okay, off! NIGHTS!