Mochi Isle
Afternoon storms · Coconut CoveScience for kidsWhy do tropical thunderstorms often come in the afternoon?
In short: The tropical sun heats the ground all morning, and warm, wet air keeps rising. By afternoon it piles up into tall storm clouds and a short, heavy thunderstorm bursts. Once the rain cools the air, the clouds fade and evenings turn clear.
How it works
In the morning the sun heats the ground, and the ground warms the air touching it. Warm air is lighter than the air around it, so it rises in bubbles, like a hot-air balloon. Tropical air is very humid, which means it is full of invisible water vapour that gets carried up too.
As the warm air rises it cools, and the vapour condenses into droplets, first forming puffy cumulus clouds. Turning vapour into droplets releases heat, which pushes the air even higher, so the cloud keeps growing like rising dough. By afternoon it becomes a towering storm cloud, called a cumulonimbus, with lightning, thunder and heavy rain.
Falling rain drags cold air down with it, cooling the ground and cutting off the supply of warm, rising air. Without its fuel, the storm cloud soon breaks up. That is why afternoon storms arrive fast and leave fast, and the evening sky is often clear again.
Where to see it in New Zealand
Daily afternoon storms are not common in New Zealand, but over the Tiwi Islands near Darwin in northern Australia, a huge thunderstorm builds almost every afternoon at certain times of year. It is so regular that it even has a nickname: Hector. On hot summer afternoons here, storm clouds sometimes tower over inland areas and mountains too.
Try it together
On a hot, sunny summer day, take a photo of the sky from the same spot every hour from morning to afternoon. Compare them: do small white clouds grow taller and darker? If you hear thunder, go inside straight away.
Kids also ask
Why do these storms come in the afternoon, not the morning?
The ground needs several hours of sunshine to reach its hottest. Warm air rises most strongly in the early afternoon, so that is when storm clouds usually finish growing.
What does a storm cloud look like?
A storm cloud is tall and thick, dark and gloomy underneath, with a top like a giant cauliflower. The very top often spreads out flat like an anvil. If one is coming closer, it is time to head indoors.
In the game, “Afternoon storms” is a nature card on Coconut Cove.
Your child finds this card by reaching the right place or meeting the right weather on the island, and lights it up by answering the question on the back. Tap the button below and the game shows your child which island it is on and how to find it. Mochi Isle is a browser learning game for ages 5 to 18; the main island and the daily lesson are free.
Find “Afternoon storms” on the island ↗ All cards from Coconut Cove