Lightning happens when electrical charges inside a storm cloud and between the cloud and the ground build up so much that the air can no longer insulate them, causing a sudden electric discharge. This discharge is what we see as a bright lightning flash and hear as thunder a moment later.

Quick Scoop

Charge build‑up in clouds

Inside a thunderstorm, strong updrafts and downdrafts make ice particles and water droplets collide, which separates electric charge: negative charges gather near the cloud base, while positive charges collect near the top.

The ground under the storm becomes positively charged, especially on tall objects like trees and buildings, setting up a powerful electric field between cloud and ground.

The spark that becomes lightning

When the electric field gets strong enough to overcome the insulating power of air, narrow channels of charge start moving: a “stepped leader” of mostly negative charge moves downward from the cloud, while “streamers” of positive charge reach upward from the ground.

When they connect, a much larger current surges along the path in a “return stroke,” which is the bright lightning bolt humans see streaking across the sky.

Types and speed of lightning

Lightning can occur within a cloud, between two clouds, or between cloud and ground, but cloud‑to‑ground lightning is what most people notice because it strikes objects at the surface.

The whole sequence—from initial charge motion to visible flash—finishes in under a second, making lightning appear almost instantaneous even though it unfolds in multiple rapid steps.

Why thunder follows lightning

Lightning superheats the surrounding air to temperatures hotter than the Sun’s surface, causing the air to expand explosively and generate a shock wave.

This shock wave travels outward as sound waves, which we hear as thunder a few seconds after seeing the flash because light reaches us much faster than sound.

Safety and quick rule

Because lightning follows paths of least resistance, it often hits tall, pointed, or isolated objects, and can then spread through the ground or nearby structures.

A widely used safety reminder is: when thunder is heard, move indoors immediately and stay away from tall trees, open fields, and metal objects, since strikes can occur even before the heaviest rain arrives.

Information gathered from public forums or data available on the internet and portrayed here.