Absent the original context (and even then...) the surviving fragments of Herakleitos can scarcely be unpacked with any assurance. To me the thought implies several aspects. There is the fairly obvious image of thunderbolt as metaphor for catastrophic/revolutionary change as basic to natural as well as social development. But also, I believe, reference to the interplanetary electric discharges that Plato (in Timaios) suggested were the "truth" behind the seeming myth of Phaeton's destruction by a thunderbolt and that Seneca (in Thyestes) called "that hand [of Jupiter] by which the threefold mass of mountains fell." Beyond which, I apprehend a much deeper cosmology--the suggestion that the whole universe is to be comprehended as an electrical, rather than a gravitational, phenomenon.
Shane