Mochi IsleWhere does morning dew come from?
In short: Dew does not fall from the sky. On clear, still nights, grass becomes colder than the air around it, and invisible water vapour in the air turns into tiny droplets on the cold leaves. That is dew.
How it works
Air always holds some invisible water vapour. Warm air can hold more of it than cold air can.
On a clear night, with no clouds overhead, the ground and the grass lose their warmth to the sky and become cooler than the air. The air touching the leaves cools down and cannot hold as much vapour, so the extra becomes droplets on the leaves.
When the sun rises, the air and grass warm up and the dew turns back into vapour and disappears. If the grass gets colder than 0 °C, the vapour turns straight into white frost.
Where to see it in New Zealand
On autumn and winter mornings in New Zealand, lawns are often covered in dew, and inland areas often get frost. Sometimes the drops on the tips of grass blades are actually water pushed out by the plant itself, called guttation, which looks a lot like dew.
Try it together
Take a glass of iced water out of the fridge and put it on the table. Do tiny droplets soon cover the outside of the glass? You can also leave an empty glass jar outside on a clear night and check it early next morning.
Kids also ask
Why is there less dew after a cloudy night?
Clouds act like a blanket, sending some of the ground's warmth back down, so the grass does not get cold enough for the vapour to form drops. Windy nights are similar, because the wind keeps bringing in slightly warmer air.
Do the drops on a cold glass leak out from inside?
No. They are water vapour from the air that turned into droplets when it touched the cold glass, the same way dew forms.
In the game, “Morning dew” 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 “Morning dew” on the island ↗ All cards in the Sky set