During lightning triggering experiments I was working on some 20 years ago, the graph of potential in kV per meter over time was a repeating sawtooth that would peak around – IIRC – 8kV per meter. By that time either we would trigger it ourselves, or it would strike within 2-3 miles and back to the bottom again. The period is foggy, but I am thinking 20-40 seconds or so was what we were dealing with at the time - I am sure that varies with the properties of the storm.

However unless you move quickly enough the through the field charge the potential rapidly equalilzes. We had to move the wire over a certain speed for it to be effective.. rockets are good for that. I'm thinking about this and combat models.. I can see some potential difference happening as you cut through an area with a fair space charge.

After watching a few triggered strikes at fairly short distance (yes in a large shielded enclosure) I decided it deserved even more respect..