I only ever shoot in RAW but I have to say, if you don't usually do this, at least put it to good use when shooting lightning. The strong contrasts are better captured in 12 or 16bit colour than they are at 8bit JPEG.
Storm season is due to start here soon as well. We've had a few through but I keep finding myself in too lazy a mood to do anything other than capture from my back windows. Most of my better storm chase shots land here:
in my gallery, including my favorite digital multiple exposure taken from home:
This was shot using the following settings for all of the required shots, all from the same static point in that space of about two minutes. Taken using very short exposure times due to the high frequency of the lightning and because of the very bright lights from the homes in the near vicinity.
EXIF:
DateTime Original: 2007:10:08 18:20:37
Digital Zoom Ratio: 1
Exposure Bias: -0.66666666666667 EV
Exposure Mode: 1
Exposure Program: Manual
Exposure Time: 1/0 sec
FNumber: f 7.1
File Source: Digital Still Camera
Flash: No Flash
Focal length: 18 mm
Gain Control: 0
ISO: 200
Make: NIKON CORPORATION
Max Aperture: f 3.5
Metering Mode: Center Weighted Average
Model: NIKON D70