Create Your Own Lightning with Photoshop

This tutorial will give you the basics to learning how to create lightning using photoshop.
We start with a blank page of your preferred aspect ratios (You can use a rectangle or square shape, I am using the Web preset 1600X1200 with transparent background.)

Once you have the new file, make sure your preset foreground and background colors are black and white. Choose the gradient tool (linear or reflected work, but for this tutorial, we will use linear.) Now make a horizontal line in the middle of the page to get this gradient:

Now use this effect only once: Filter > Render > Difference Clouds
Then Command (or Ctrl) + I to invert
This is what we have so far:

To make it darker, bring up the Levels box by clicking on Command (or Ctrl) + L
I used these presets to make the most realistic lighting, but what you need to do is bring the middle gray cursor to the right so that you can darken the mid-tones, and also darken the shadows (the black cursor on the left) a little bit.

We are almost done, all we need to do is to bring this thunder to life through a hint of color. To do so, go to Image > Adjustment > Selective Color. Choose the Neutrals colors, here, it is completely up to you to choose the color of thunder that is most pleasing to your purpose, and these are the setting I used to colorize my lightning:

Click OK, and you have lightning.

I hope you enjoyed this tutorial, and hope to see you rock the earth with your own lightning and thunder.