Here's something that trips most people up: Earth is actually slightly closer to the Sun in January than in July. So why is January freezing and July boiling (if you're in the UK, "boiling" means 22°C and everyone loses their mind)?
The answer is tilt. Earth spins on an axis — an imaginary pole running through the North and South Poles. That axis isn't straight up and down; it leans at about 23.5 degrees. And as Earth travels around the Sun over a year, that tilt means different parts of the planet get hit by sunlight at different angles.
Shine a torch straight down onto a table. You get a bright, concentrated circle of light. Now tilt the torch so it hits the table at an angle — the same amount of light spreads over a much bigger area, so any one spot gets less of it. That's exactly what happens in winter: sunlight arrives at a shallow angle, spreads over more ground, and delivers less heat per square metre.
Why is summer warmer?
In summer (for the Northern Hemisphere, that's June to August), the North Pole is tilted towards the Sun. Sunlight hits at a steeper angle — more concentrated, more heating power per square metre. The days are also longer, so the ground has more hours to absorb heat. In winter, the North Pole tilts away, sunlight arrives at a shallow angle, and days are short. Less heat, shorter days — winter.
What about places near the equator?
At the equator, sunlight always hits at roughly the same steep angle all year round, so there's not much temperature change between seasons. Instead, equatorial regions tend to have wet and dry seasons — driven by shifting wind and rain patterns — rather than hot and cold ones.
What are the solstices and equinoxes?
The summer solstice (around 21 June in the UK) is the longest day — Earth's North Pole is tilted as far towards the Sun as it gets. The winter solstice (around 21 December) is the shortest day — tilted as far away as possible. The equinoxes (March and September) are the two points where neither pole is tilted towards or away, and day and night are roughly equal length across the whole planet.
Here's something that surprises most people. Earth is actually closer to the Sun in January than in July. So why is January freezing and July hot?
The answer is tilt. Earth spins like a spinning top on an invisible pole. This pole goes through the North and South Poles. But the pole isn't straight up and down. It leans at 23.5 degrees to one side.
As Earth travels around the Sun during the year, this tilt is very important. Different parts of our planet get hit by sunlight at different angles.
Think about shining a torch straight down onto your desk. You get a bright, small circle of light. Now tilt the torch so it hits your desk sideways. The same light spreads over a much bigger area. Each spot on your desk gets less light. This is exactly what happens in winter. Sunlight comes at a sideways angle and spreads out more. So each bit of ground gets less heat.
Why is summer warmer?
In summer, the North Pole is tilted towards the Sun. This happens from June to August in Britain. Sunlight hits us at a steeper angle. It's more concentrated, like the torch pointing straight down. This gives more heating power to each bit of ground.
Summer days are also longer. The ground has more hours to soak up heat from the Sun. In winter, the North Pole tilts away from the Sun. Sunlight comes at a sideways angle and days are short. Less heat and shorter days make winter cold.
What about places near the equator?
At the equator, sunlight always hits at the same steep angle. It's like having the torch pointed straight down all year. So there isn't much temperature change between seasons.
Instead of hot and cold seasons, these places have wet and dry seasons. This happens because wind and rain patterns change during the year.
What are the solstices and equinoxes?
The summer solstice happens around 21 June in Britain. This is the longest day of the year. The North Pole is tilted as far towards the Sun as it can get.
The winter solstice happens around 21 December. This is the shortest day. The North Pole is tilted as far away from the Sun as possible.
The equinoxes happen in March and September. At these times, neither pole is tilted towards or away from the Sun. Day and night are the same length everywhere on Earth.