If it's too low early morning, this possibly is not taking place, so glucose drops too low. If this is occurring, I suggest you try taking 4000 to 8000mg/day glutamine at night. This amino acid can be used by the brain in place of glucose, but being an amino it doesn't cause a sharp drop in blood glucose levels.
Sometimes, heat lightning isn't lightning at all, but a cloud reflection of lightning from a very distant storm. In other instances, it is regular lightning which has formed far off in the distance, making a flash instead of a recognizable lightning bolt.
The thunderstorm could be miles away. The ice or water particles in the cloud may not be large enough to fall, therefore creating electricity. Lightning is hotter than the surface of the sun, so it superheats the air and causes a sonic boom, the thunder. It is very possible, it is actually called dry lightning and can be very rare.