Mochi IsleWhy do rain clouds look grey or dark?
In short: Clouds are made of countless tiny water droplets or ice crystals. Thin clouds scatter sunlight and look white, but rain clouds are so thick that most sunlight bounces back out of their tops and sides, so they look grey or dark from below.
How it works
A white cloud is made of many tiny droplets that scatter sunlight in every direction. All the colours are scattered together, so the cloud looks white.
As a cloud grows thicker, sunlight bounces around inside it so many times that most of it goes back out of the top and sides. Little reaches the base, so from underneath it looks grey or even black.
So a dark cloud is not dirty. It is the same stuff as a white cloud, just thicker and wetter. When the drops grow too heavy for the air to hold up, they fall as rain.
Where to see it in New Zealand
New Zealand's weather can change quickly, and westerly winds often carry moist air in from the Tasman Sea, especially to the west of the country. When clouds to the west grow thicker and darker, rain is often not far away.
Try it together
Take a photo of the sky on a sunny day and another on a cloudy day, then compare white clouds with dark ones. Before rain, watch whether the clouds get lower and darker.
Kids also ask
How do clouds stay up in the sky?
Cloud droplets are tiny, much thinner than a hair, so rising air can hold them up. When droplets bump together and grow too heavy, the air can no longer hold them and they fall as rain.
What kind of cloud brings thunder?
Thunderstorms usually come from cumulonimbus clouds. They tower like tall, thick mountains, and inside them ice crystals and soft hail collide, building up the electric charge that makes lightning.
In the game, “Rain clouds” is a nature card from the Sky set, and it can turn up on any island.
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 “Rain clouds” on the island ↗ All cards in the Sky set