Does Earth being closer to the Sun cause summer?

No — this is the most common misconception about seasons. Earth's orbit is slightly elliptical, and Earth is actually closest to the Sun in early January (perihelion, ~147.1 million km) and farthest in early July (aphelion, ~152.1 million km). This small distance difference (about 3%) has a negligible effect on temperature compared to the large effect of axial tilt. The NASA Space Place seasons page explains this with clear diagrams.

Why do the Northern and Southern hemispheres have opposite seasons?

Earth's axis tilts at 23.5° relative to its orbital plane — and it always points in the same direction (toward Polaris). When the Northern Hemisphere is tilted toward the Sun (June solstice), sunlight strikes it at a steeper angle and days are longer — summer. At the same moment, the Southern Hemisphere is tilted away, receiving more oblique sunlight and shorter days — winter. Six months later the geometry reverses. The ESA Kids seasons page shows the orbit diagram clearly.

What are the solstices and equinoxes?

The solstices (around 21 June and 21 December) are the points in Earth's orbit where one hemisphere's axial tilt toward the Sun is at its maximum — giving the longest day (summer solstice) and shortest day (winter solstice). The equinoxes (around 20 March and 23 September) are when Earth's axis is perpendicular to the Sun–Earth line, so every location on Earth experiences approximately 12 hours of daylight and 12 hours of darkness. The word "equinox" comes from Latin for "equal night". Precise dates shift slightly each year because the calendar year and orbital year differ slightly.

Why are days longer in summer?

In summer, the hemisphere tilted toward the Sun has a larger arc of its daily rotation in sunlight. Sunrise is earlier and sunset is later. At the June solstice, the Arctic Circle experiences 24 hours of daylight (the "midnight sun") and the Antarctic Circle has 24 hours of darkness. Near the equator, day length varies little year-round because equatorial locations are always roughly perpendicular to the Earth–Sun line. This directly explains why summer is warm: more hours of daylight means more total solar energy absorbed. Read more about how Earth–Moon geometry works in our Moon phases guide.

How the Seasons Work — Guide

Why tilt matters

Earth's rotational axis is tilted 23.5° relative to the plane of its orbit around the Sun. This tilt is fixed in space — it always points toward the same direction (roughly toward the North Star, Polaris). As Earth orbits the Sun over a year, the Northern Hemisphere is tilted toward the Sun for one half of the orbit and away from it for the other half.

When tilted toward the Sun, two things happen simultaneously: sunlight hits the surface at a steeper (more direct) angle — so the same beam of sunlight heats a smaller area — and days are longer, giving more time for heating. Both effects combine to produce summer. The reverse conditions produce winter.

Summer

Hemisphere tilted toward Sun
Sunlight more direct (less spread)
Longer days, more heating time
Higher Sun angle at noon

Winter

Hemisphere tilted away from Sun
Sunlight oblique (spread over more area)
Shorter days, less heating time
Lower Sun angle at noon

The angle effect

Imagine shining a torch directly down onto a table versus shining it at a shallow angle. The same light beam covers a much larger area when angled — so the illuminated patch is dimmer. This is exactly what happens with sunlight in winter: the same solar energy is spread over more ground, so each square metre receives less. In midsummer in London, the Sun at noon reaches about 62° above the horizon; in midwinter it reaches only about 15°. This geometric effect accounts for most of the temperature difference between seasons.

The geometry of Earth's orbit also explains why we can see the Moon's phases change — both are a consequence of the same Sun–Earth–Moon orbital relationships.

How the seasons work

Why tilt matters

The angle effect

Frequently asked questions