It just keeps on raining---another way to create a thunderstorm is in the offing. On your original image, create a new layer, fill with black and use similar settings from the first rain tutorial: Filter > Add Noise > 340, Filter > Motion Blur > Angle > 65, Distance > 10 pixels. Change the Blending Mode to Screen on the new layer.

To get more in the dark and gloomy mood of a rainstorm, press Cntrl + L to access Levels. Change the first Input Level to 150.

That is definitely more like it. To rid the image of the spots on the image sides, use Cntrl +T (Free Transform) and stretch out until gone.

You could stop right here, although if your image is too bright, click on the original image layer and access Cntrl +L once again. This time, change the far right Output Levels box to 198.

Experiment with the various Level settings to achieve the effect you wish. In the meantime, there you are...another rainstorm.