Dark lightning and Heat lightning

Heat lightning and dark lightning are semantically related In some cases you can replace phrase "Heat lightning" with "Dark lightning", this phrases are similar.

Heat lightning noun - Bright flashes of light near the horizon without thunder (especially on hot evenings); usually attributed to distant lightning that is reflected by clouds.

Dark lightning and heat lightning are semantically related in summer lightning topic. You can use "Dark lightning" instead a noun phrase "Heat lightning".