lightning is light you can measure it but you cant way it

very hard to grasp this type of question,,,,but i'am sure some bright spark will come up with a good answer,,,shed some light on it !! so to speak ,,,,if only for a second or two,,,,,

Not my speciality but I'll give it a go. First some ground rules. Obviously lightning bolts vary greatly in size and power. So to do a calculation for all would be very difficult. We'd have to put some definitions in place (e.g. for a bolt x metres long, with current y etc). Also as for the air that is affected by the discharge where do we draw the line and say "this is the boundary of the bolt"? I think you can take the diameter to be around 10^-2 metres across. Complete guess I am afraid. The length I dunno maybe 3000m? Again complete guess. You could I suppose work out the mass involved from there given average air densities and so on. The light given off is massless (photons have zero mass) therefore will 'weigh' nothing. So I suppose you could define an arbitrary cut off point for the bits I have listed above and then calculate the mass of the air involved from there. Alth0ough is that really the lightning? Lightning is an electrical discharge so maybe even speaking of it having a mass as such doesn't really make sense, perhaps? You could look at the air affected and calculate from there but I am too tired to do anything like that right now.

There are a billion trillion electrons in a lighting bolt times the atomic mass of an electron which is 9.10938215(45)×10^−31 kg, this equals a very tiny number.

Since it's a form of light ... it should be light ... I suppose.