THE TILT
Leaning at 23.4°
The Royal Observatory says Earth's axis is tilted 23.44°. When the north leans towards the Sun, it gets more direct light and longer days.
How it works
WHAT THE SCIENCE SAYS
It's the tilt,
not the distance.
Earth is closest to the Sun in January.
That surprises most people. Seasons come from Earth's tilted axis, which leans one hemisphere towards the Sun for half the year and away for the other half, changing both the angle of sunlight and the length of the day.
23.4° the tilt that makes seasons
Check a date- Tilt makes seasons
- Solstices set the day length
- Weather lags behind
- The year, explained
THE SHORT ANSWER
One leaning planet,
four seasons.
The axis always points the same way in space.
As Earth orbits, each hemisphere takes its turn.
THE SOLSTICES
Longest and shortest days
The solstices are the moments a hemisphere is most tilted towards or away from the Sun. In 2026 the winter solstice falls on 21 December.
See the numbers
TWO CALENDARS
Winter starts twice
Astronomers start seasons at solstices and equinoxes. Meteorologists use whole months: winter is December, January and February.
Check a date
FOUR THINGS TO REMEMBER
Reading the
seasons right.
A few ideas clear up most of the confusion about when seasons start and why they feel the way they do.
It is not about distance
Northern winter happens when Earth is closest to the Sun, NASA points out.
A solstice is a moment
The solstice is an exact moment in time, when a hemisphere is most tilted towards or away from the Sun.
Warmth lags light
Oceans and air take time to heat and cool, so the hottest and coldest weather comes after the solstices.
Hemispheres swap
When it is summer in the north, it is winter in the south, because the South Pole is then tilted away.
TWO NUMBERS WORTH KNOWING
A small lean,
a big difference.
The angle behind every season,
and what it does to a London day.
23.44°
Angle of Earth's axis
The Royal Observatory says Earth's axis of rotation is tilted at 23.44° to its orbit, so each hemisphere spends half the year leaning towards the Sun.
THE TILT · ROYAL OBSERVATORY
8h 49m
Longest minus shortest day, London
London's shortest day lasts 7 hours 49 minutes and 42 seconds, 8 hours 49 minutes shorter than the day of the summer solstice.
DAY LENGTH · ROYAL OBSERVATORY
NASA notes Earth is about 91.4 million miles from the Sun at its closest, in January, and 94.5 million miles at its farthest, in July: too small a change to cause the seasons.
A QUICK DATE CHECK
What happens
on this date?
Pick a date to see what it marks in the astronomical or meteorological year. The bar shows how much daylight the UK gets around then.
Based on the Royal Observatory Greenwich and the Royal Meteorological Society. Solstice and equinox dates can shift by a day or two.
WHY THE SHORTEST DAY IS NOT THE COLDEST
The light peaks
before the heat.
In summer the Sun climbs higher and stays up longer, so sunlight arrives more directly and for more hours. In winter the glancing angle and short days let the air stay cold.
The Royal Observatory explains that the atmosphere and especially the oceans take time to warm up and cool down. That lag is one reason meteorologists start summer on 1 June and winter on 1 December, rather than at the solstices.
Questions
Questions people ask
Why do we have seasons?
Because Earth's axis is tilted. NASA says that when the North Pole tilts towards the Sun it is summer in the Northern Hemisphere, and when the South Pole tilts towards it, it is winter in the north.
Is Earth closer to the Sun in summer?
No. NASA says Earth is closest to the Sun in January and farthest in July, and the difference in distance does not make much difference to our weather.
When does winter officially start?
It depends who you ask. Astronomical winter begins at the December solstice; meteorological winter begins on 1 December and runs to the end of February.
Why do the solstice dates change?
The Royal Meteorological Society says a full orbit is not exactly 365 days and the orbit is elliptical, so solstice and equinox dates can shift by a day or two.
What does solstice mean?
It comes from the Latin solstitium, meaning 'Sun stands still', because the Sun's path in the sky stops moving north or south before changing direction.
Sources
- Royal Observatory Greenwich: What is the summer solstice?
- Royal Observatory Greenwich: When is the winter solstice? The shortest day
- Royal Meteorological Society: The difference between meteorological and astronomical seasons
- NASA Space Place: What causes the seasons?
Updated