What are heat domes and how do they happen? | CBC Kids News

Added: 2026-05-28

[00:00:00]To understand heat domes, let's boil some water.

[00:00:04]Just hear me out.

[00:00:06]When the steam from the boiling pot rises, heat escapes. But, if you put a lid on it, the air gets trapped. It hits the lid and gets pushed back down, and the inside of the pot gets hotter and hotter much faster.

[00:00:23]And that is what a heat dome does. It puts the air beneath it under pressure.

[00:00:28]I'm going to get to how a heat dome affects you [music] and me. But first, let me explain how the space around us gets turned into this boiling pot. We know that air has mass. When it's packed into a bicycle tire, it can hold you up.

[00:00:41]But even the air around you has weight.

[00:00:44]What we call atmospheric pressure is just the weight of all the molecules in the atmosphere pressing down on the Earth's surface. But this pressure isn't the same everywhere. Our atmosphere is always on the move.

[00:00:57]Low pressure systems pull air upwards, bringing clouds and storms. High pressure systems pull air downward and usually bring clear skies. When all that air is being pushed downwards, it gets compressed, and that makes [music] the air warmer.

[00:01:14]These pressure systems are pushed along by the jet stream.

[00:01:18]Think of the jet stream like a river of air flowing high above us from west to east.

[00:01:24]But just like a river, it doesn't move in a straight line. It bends and curves.

[00:01:29]Sometimes, a big bulge of warm air pushes up from the south and blocks the jet stream. When that happens, a high pressure system can get stuck [music] in one place. This parked high pressure system is the lid in our boiling pot analogy. Heat can't escape easily, so it builds day after day into a heat dome.

[00:01:51]Sometimes, this pattern is called an omega block because it It like the Greek letter omega on the weather map. A big high pressure bubble trapped between two low pressure systems.

[00:02:03]Remember when I said air is always on the move?

[00:02:05]This system is not going anywhere.

[00:02:09]Now, trees and grasses will reflect sunlight and release moisture to try to cool things down, but prolonged heat will dry out the landscape.

[00:02:18]In towns and cities, it's even worse.

[00:02:20][music] Concrete, brick, and asphalt are heat sponges. They soak up the heat during the day and slowly release it at night, never giving the city or its people a chance to cool down.

[00:02:32]For us, no break from high temperatures can lead to dehydration, heat stroke, and in severe cases, even death.

[00:02:40]Reaching for a glass of ice cold lemonade might not be enough relief during a heat dome.

[00:02:46]So, here's four things you can do to stay safe.

[00:02:49]One, drink lots of water. Two, head indoors for the hottest moments of the day. Three, if you have to be outside, wear light clothing, carry a water bottle with you, and avoid too much physical activity.

[00:03:03]Four, if you don't have air conditioning, look for cooling centers or a public library near you.

[00:03:09]Eventually, a heat dome will lose its grip and cooler air from the west will mix with it and flush it out. But, that relief comes with a catch. After days of baking heat, the ground is dry.

[00:03:23]When those new winds arrive, they act [music] like a giant fan on a campfire, making it much easier for wildfires to spread.

[00:03:31]While no single weather event can be blamed on climate change, scientists agree that as the weather warms, extreme heat events, >> [music] >> like heat domes, are becoming more frequent, more intense, and longer-lasting.

[00:03:45]But, you can beat the heat if you are prepared.

[00:03:49]To find out For about extreme nature events, check out cbckidsnews.ca.

[00:03:54]For CBC Kids News, I'm Jana Cay Hoskins.

[00:03:57]Stay cool out there.