The British Isles covers a large area and for that reason has a highly variable climate.  We can consider the high range in weather and climate types over time and space, and at different scales.  The British Isles includes all of the Northern Scottish Islands including the Shetland and Orkney Islands, the Western Isles of the Outer Hebrides out in the Atlantic Ocean, down towards the South and the Channel islands which hug the coast of Northern France.  They also include the island of Ireland, the Scilly Isles off the South West of Cornwall as well as the varied geography of mainland Britain which is home to England, Scotland and Wales.  This means that the British Isles cover a latitude range of 49°N in the Channel isles all the way up to 60°30’N at the Shetland Isles.  They also cover a longitudinal range2°E in Norfolk to 10°W on the West coast of Ireland.  Couple this with the varied and diverse geomorphology of the British Isles and it is understandable as to why Climate and Weather can be VARIABLE.

 Overall, there are identifiable patterns in Britain’s weather and climate;

• It is wetter in the west and in the upland areas  (such as the Pennines and Grampians) than it is in the East.
• It is colder in the North than it is in the South
• There is more snowfall in the North and East of Britain
• The winds are stronger in the West of Britain
• Temperatures tend to be milder in the West of Britain.

There are several reasons for these patterns – It is wetter in the West and uplands of Britain because of relief rainfall, the prevailing winds that hit the UK and the passage of depressions systems.  Relief Rainfall is a dominant process, and is coupled with the fact that Britain’s prevailing (dominant) wind direction is from the South West.  Precipitation is caused when moist air rises and cools at the DALR.  The air reaches saturation point or Dew point and water droplets form around pollen or dust particles.  These water droplets are tiny, and coalesce or collide to form larger droplets.  In the case of sub zero temperatures, it is ice crystals that form and join together in the ice crystal mechanism proposed by Bergeron and Findeisen. When the water droplets or ice crystals in clouds grow to a certain size, gravity causes them to fall because of their own weight.  Relief rainfall is a dominant method of precipitation formation in the UK and relates to the precipitation that is created as air masses are pushed up and over mountainous or upland areas.  Relief rainfall occurs where moist air is forced to rise over a physical barrier such as a mountain range. Warm air is carried to the West coast of Britain by our prevailing (dominant) winds, the South Westerlies. This air encounters the high land on the coast of Ireland, then the Lake District and the Pennines and it is forced to rise above this barrier. As it rises, the warm air cools with height at a rate of 9.8°C per 100om (the DALR). As the air cools water vapour condenses to form clouds and eventually it rains over Britain's highland areas. As the air descends to the East coast of Britain or the Lee slope it warms slightly and there is less rainfall. This results in a rain shadow on Britain’s east coast.  It is for this reason that the West coast of Britain is wetter than the East, Blackpool receives 950mm of rainfall per year, The Pennines 2000mm+, and Newcastle 700mm.  The West of Britain is also the first affected by most depression systems, which tend to swing south west to north east over The British Isles.  This is also the reason why winds are stronger in the west.

 It is colder in the North than the South because of the impact latitude has on temperature, and a full explanation of this can be found here.  Temperatures also tend to be milder in the West than the east because of Ocean currents, the West receives the full benefits of the warming Gulf Stream and tropical maritime air masses, whilst the East gets a cold sea current from the Atlantic Ocean which passes into the North sea (the reason for the famous North East coast sea Fret – warm air passes over the cold North sea, is cooled, which forces condensation and the formation of mist, known locally as fret!). 

There is more snowfall in the East and North of the country because it is colder in the north due to latitudinal differences but also because of the air masses that affect these locations.  The East coast can receive Polar continental air masses in winter which are bitterly cold and pick up moisture on the final part of their journey from Eastern Europe across the Baltic Sea and the North Sea.  This moisture is then dumped as snow on the East coast of Britain.  The Northern parts of Britain are vulnerable to Arctic Maritime air masses from the Arctic regions, which also bring snow.

The weather across Britain is therefore highly variable, the Western isles benefit from the warm passage of the Gulf Stream but are exposed to uninterrupted winds across the Atlantic, the fury of depressions year round and lower temperatures due to their high latitude.  Newcastle is drier and a little warmer, and is spared the worst of rainfall and storms being in the shadow of the Pennines.  However, it suffers polar continental air masses, the risk of snow, sea fret from its cold sea current and colder temperatures than places in the south of the country.  One thing that is sure is that the British Isles has varied weather and climate and it is never dull!