Climate of the United Kingdom

Since the UK is always in or close to the path of the polar front jet stream, frequent changes in pressure and unsettled weather are typical.

Northern Ireland, Wales and western parts of England and Scotland, being closest to the Atlantic Ocean, are generally the mildest, wettest, and windiest regions of the UK, and temperature ranges there are seldom extreme.

England is also sunnier throughout the year than Wales, Northern Ireland and Scotland, the sunniest month is July, with an average of 193.5 hours.

[3] The climate of south-west England displays a seasonal temperature variation, although it is less extreme than most of the United Kingdom with milder winters.

Gales are less common in England compared to Scotland; however, on some occasions, there can be strong winds, and rarely, the non-tropical remains of Atlantic hurricanes and tropical storms.

Rare summer heatwaves of 28 °C+ occur on occasion, but sustained is uncommon, due to the high latitude and cool maritime climate.

[28] Temperatures in Wales remain higher than would otherwise be expected at its latitude because of the North Atlantic Drift, a branch of the Gulf Stream.

As well as its influence on Wales' coastal areas, air warmed by the Gulf Stream blows further inland with the prevailing winds.

Greater London, Kent, Sussex, Surrey, Essex, Hertfordshire, Cambridgeshire, Suffolk and Norfolk see the most thunderstorms during the summer.

On rare occasions, a type of supercell thunderstorm called the Spanish Plume forms over the country after very hot weather.

Such events are aided by the surrounding Atlantic Ocean and seas being at their warmest, keeping the country in warm air, despite the relatively weak sun.

Frequently in the mountains potent depressions may move in from the north in the form of "polar lows", introducing heavy snow and often blizzard-like conditions to parts of the United Kingdom, particularly Scotland.

During periods of light winds and high pressure, frost and fog can become a problem and can pose a major hazard to drivers.

[28] Generally the United Kingdom sees frequent cloudy skies due to its high latitude and oceanic controlled climate.

The counties of Dorset, Hampshire, Sussex and Kent are the sunniest areas, which have annual average totals of around 1,750 hours of sunshine per year.

Radiation fog may develop over inland areas of Great Britain and can persist for hours or even days in the winter and can pose a major hazard for drivers and aircraft.

The subsided, dry air from the Azores often results in clear skies and few clouds, bringing frosty nights in winter and warm days in the summer.

These warm ocean currents also bring substantial amounts of humidity which contributes to the notoriously wet climate that western parts of the UK experience.

The wettest spot in the United Kingdom is Crib Goch, in Snowdonia, which averaged 178 inches (4,500 mm) rain over a 30 year period.

[61][62] Most rainfall in the United Kingdom comes from North Atlantic depressions which roll into the country throughout the year from the west or southwest and are particularly frequent and intense in the autumn and winter.

Parts of England are dry in global terms, which is contrary to the stereotypical view—London receives just below 650 millimetres (25.6 in) per annum,[63] which is less than Rome, Sydney, or New York City.

July 2006 was the hottest month on record for the United Kingdom and much of Europe,[65] however England has had warmer spells of 31 days which did not coincide with a calendar month—in 1976 and 1995.

[67] Generally, the United Kingdom has cool to mild winters and warm to hot summers with moderate variation in temperature throughout the year.

In England the average annual temperature varies from 8.5 °C (47.3 °F) in the north to 11 °C (51.8 °F) in the south, but over the higher ground this can be several degrees lower.

[54] Temperatures tend to drop lowest on late winter nights inland, in the presence of high pressure, clear skies, light winds and when there is snow on the ground.

[70] The United Kingdom is not particularly noted for extreme weather, as the region's cool, oceanic climate is opposed to convective storms.

The counties that see the most storms are Kent, the eastern part of Surrey, Sussex, Greater London, Essex, Cambridgeshire, Hertfordshire, Suffolk, Norfolk and to a lesser extent Lincolnshire and Nottinghamshire.

[72] Occasionally, thunderstorms can be severe and produce large hailstones as seen in Ottery St Mary, Devon in October 2008, where drifts reached 1.8 metres (5 ft 11 in).

During this period the temperature was so low that much of the surrounding ocean froze and a great ice sheet extended over all of the United Kingdom except the south of England (connected to mainland Europe via the dry English Channel) and southern coastal areas of Wales.

While some of this may be due to a recovery from the cooler period of climate mid 20th century (particularly the 1960s) the last 20 years has nonetheless seen an unprecedented level of warm weather.