Last night I was out shooting thunderstorm, here is some of the results. I also included som advice when taking these storm. As a motive they are incredible rich, but taking them easily putting you in harms way.
Safety, First and foremost – lighting is dangerous! Not only lighting but the heavy rain and hail that comes with it, so make sure you are aware and safe!
Planning, stay informed. Which direction is the weather moving. Planning is essential when positioning yourself, both safe and with an interesting forground. I am using lightningmaps.org for planning where to be.
Equipment, Besides your camera, all you need is a Tripod, fairly wide lens (24mm’ish), remote shutter control or interval meter. in addition Camera rain protection is a good thing.
Settings, You will want to set an exposure time for between 20 and 30 seconds. Try to make your settings so the frame without lightning will be totally black. The settings I find that usually work for me are around f/4.5, ISO100 and 30sec for lighting that is somewhat in the distance. I might go as high as f/8 if they are fairly close by.