What's the difference between weather and climate?
Weather is what is happening now -- whether it is raining, or windy, or cold (or all three
together).
Climate is the average weather conditions over a long period of time -- usually about
30 years.
Often the two things that geographers focus on about climate is temperature and precipitation
Precipitation is weather than falls out of the sky -- rain, snow, hail etc.
The Meteorological Office, usually called the Met Office for short, is the UK's weather
service.
As well as forecasting what the weather is likely to be each day, it also records masses
of data about the weather from measuring stations all over the UK.
These data provide the long term averages that tell us what the UK's climate is.
The Met Office has records for the whole UK going back over a hundred years, and for some
parts of the country there are records about the British weather going back to the 17th
century!
Our current climate period is from the early 1980s to the present: 30 years.
These data can be looked at in lots of different ways -- maximum temperatures in June in Southern
England, days with more than 10mm of rain in January, and many more.
Let's just look at the very top level of data for temperature and rainfall.
This map is for the average yearly temperature in the UK for a period from 1981 to 2010.
You can see that the south of the UK is, on average, a lot warmer than the north of the
UK.
Higher parts of the UK -- for example the mountains of Wales -- are colder than lower
parts of the UK -- for example, East Anglia.
This Met Office map shows the average annual rainfall for the UK for the period 1981 to
2010.
As you can see, the west of the UK gets a lot more rain than the east of the UK.
The mountainous areas in the west also get the most rain of all.
Why does the UK have the climate it does?
The three main factors are our latitude, our being right next to the Atlantic Ocean and
that we are an island.
The closer a country is to the equator, the hotter the climate is.
As we are quite far north, the UK has a cool climate -- known as temperate: neither very
hot nor very cold.
Because we are close to the sea we have a maritime climate -- that means influenced
by the sea.
The sea takes longer to warm up than the land but it retains heat for longer.
That means the UK has warm summers rather than really hot summers, and cool winters
rather than really cold ones.
Being a small island increases this maritime effect.
There is also an important ocean current that affects the UK's climate.
Called the North Atlantic Drift it carries warm water from near Florida up towards Europe
and these warmer ocean temperatures make the UK warmer than it would be without this current.
Being near the sea also affects the UK's precipitation.
While some countries have a wet season and a dry season, we have rain all year because
the prevailing winds in the UK bring warm, moisture-rich air from the Atlantic.
Unstable weather conditions called Atlantic depressions form in the Atlantic ocean and
travel eastwards towards Britain, carrying warm, moist air with them.
This air hits the west of Britain first and that is why the west is wettest.
When warm, moist air is forced up and over mountains it cools down and cannot hold as
much moisture.
That accounts for the mountainous regions of the north and west of the UK getting the
most rain of all.
By the time the air reaches the east of the UK, it has lost a lot of its moisture already.
And that is why the east of the UK is drier than the west.
Being near the sea also affects the UK's precipitation.
While some countries have a wet season and a dry season, we have rain all year because
the prevailing winds in the UK bring warm, moisture-rich air from the Atlantic.
Unstable weather conditions called Atlantic depressions form in the Atlantic ocean and
travel eastwards towards Britain, carrying warm, moist air with them.
This air hits the west of Britain first and that is why the west is wettest.
When warm, moist air is forced up and over mountains it cools down and cannot hold as
much moisture.
That accounts for the mountainous regions of the north and west of the UK getting the
most rain of all.
By the time the air reaches the east of the UK, it has lost a lot of its moisture already.
And that is why the east of the UK is drier than the west.
A final factor that influences the UK's climate is connected to air masses.
Air masses are large bodies of air that develop over one region and then move across another
region.
The UK is affected by five main air masses, which helps explain why our weather can be
so variable!
The Tropical Maritime air mass forms over the warm waters of the mid-Atlantic.
This air mass brings warm and wet weather to the UK.
The Tropical Continental air mass forms over southern Europe and North Africa.
This air mass brings warm and dry conditions with it.
The Polar Continental air mass forms over northern Europe and carries cold and dry air
with it.
The Polar Maritime air mass is formed over the North Atlantic and this brings cold and
wet weather to the UK.
The Arctic Maritime air mass forms over the Arctic Ocean and this air mass is very cold.
It can be dry air but it can also combine with other weather systems to bring heavy
snow.