CABBAGETREE.KIWI / LIGHTNING THUNDER WEATHER GUIDE
Lightning & Thunder Weather Guide
A local guide to lightning, thunder, and storm safety along the Tokomairiro coast.
What Is Lightning?
Lightning is a giant electrical spark that forms when electrical charges in the atmosphere build up and suddenly discharge. Air normally acts as an insulator between positive and negative charges, but when the charge becomes strong enough, the air breaks down and a lightning bolt forms.
Lightning can occur within a single cloud, between clouds, between a cloud and the air around it, or between a cloud and the ground. It is one of the oldest and most dramatic natural phenomena on Earth.
Main Types of Lightning
- Intra‑cloud lightning — flashes within a single thunderstorm cloud.
- Cloud‑to‑ground lightning — the classic bolt that strikes the Earth.
- Cloud‑to‑air lightning — lightning that exits the cloud into clear air.
Lightning Beyond Thunderstorms
Lightning can also be seen in volcanic eruptions, intense forest fires, nuclear detonations, heavy snowstorms, and large hurricanes. Anywhere strong charge separation occurs, lightning is possible.
What Causes Thunder?
Thunder is the sound created by lightning. A lightning bolt heats the surrounding air to around 50,000 °F, much hotter than the surface of the Sun. This extreme heating causes the air to expand explosively, creating a shock wave that we hear as thunder.
Thunder can be heard up to around 25 miles away, but the sound changes with distance. Close lightning can sound like a sharp crack or bang, while distant lightning often produces a low, rolling rumble.
Count the seconds between the lightning flash and the sound of thunder:
- Seconds ÷ 5 ≈ distance in miles
- Seconds ÷ 3 ≈ distance in kilometres
If thunder occurs within about 30 seconds of the flash, the lightning is close enough to be dangerous.
Where Does Lightning Strike?
Most lightning flashes begin inside a thunderstorm cloud. If a flash is going to strike the ground, a channel of ionised air moves downward from the cloud. When it gets close to the surface, tall objects such as trees, buildings, or hills can send up upward leaders to meet it. When they connect, a powerful current flows along the channel.
Tall objects are more likely to be struck, but lightning can still hit open ground, paddocks, or beaches even when trees or buildings are nearby.
What Causes Lightning?
Inside thunderstorms, small hail‑like particles called graupel collide with smaller ice crystals. These collisions transfer electrical charge:
- Graupel tends to gain negative charge in colder regions of the storm.
- Smaller ice crystals gain positive charge and are carried higher by updrafts.
This process builds up large charge regions inside the cloud:
- An upper positive charge region (ice crystals)
- A middle negative charge region (graupel)
- A smaller lower positive region at warmer levels
When the electric field becomes strong enough, lightning forms to equalise the charge.
Types of Lightning
Cloud‑to‑Ground (CG)
The classic lightning bolt that strikes the Earth. Most CG flashes are negatively charged, but rarer positive flashes can be much more powerful and dangerous.
Intra‑Cloud (IC)
Flashes that stay within a single cloud. These are the most common type and often appear as bright flickers lighting up the cloud from within.
Cloud‑to‑Air
Lightning that exits the cloud into the surrounding clear air, often seen as branching bolts reaching out from the sides of a storm.
Positive Lightning
Lightning that originates from the top of a storm and carries positive charge. It can strike many kilometres away from the main rain area and pack a stronger punch.
Sprites, Jets & Elves
Exotic forms of lightning that occur high above thunderstorms in the upper atmosphere. They are fascinating to watch but not a direct hazard at ground level.
Global Lightning Hotspots
Lightning is most common in warm, humid regions where thunderstorms form frequently. Some of the world’s lightning hotspots include:
- Lake Maracaibo, Venezuela — famous for almost nightly lightning displays.
- Central Africa — especially the Congo Basin