The winter of 2009–2010 in Europe was unusually cold. Globally, unusual weather patterns brought cold, moist air from the north. Weather systems were undergoing cyclogenesis from North American storms moving across the Atlantic Ocean to the west, and saw many parts of Europe experiencing heavy snowfall and record-low temperatures. This led to a number of deaths, widespread transport disruption, power failures and postponed sporting events.

Cause The cold weather was caused by high pressure over Greenland and Iceland forcing weather patterns southward, a phenomenon described by meteorologists as the Arctic oscillation and also the North Atlantic oscillation which were negative compared to normal. The North Atlantic oscillation in Winter 2009/10 was lower than during any winter in over a century and this resulted in more easterly winds bringing cold air into Northern Europe from Siberia and the Arctic. Scientists have shown that El Niño, the quasi-biennial oscillation and solar variability all conspired to drive this extreme winter.

December 2009

16–21 December

Light snowfall occurred in the UK on 16 December and weather warnings were given on most local TV stations; there were some traffic jams towards the south. The snow later spread towards France and northern Spain. In mainland Europe, early snowfall was seen across much of the western half of the continent. On 17 December, the Swiss canton of Grisons saw a record-low overnight temperature of −32 °C (−25.6 °F). This snowfall led to the shutdown of Utrecht Centraal (the largest rail hub in the Netherlands). While snowfall on highways led to the busiest morning rush hour of 2009, with a total of 671 km (417 m) in traffic jams. The following day, heavy overnight snowfall caused widespread disruption across large parts of the South East, East Anglia, the East Midlands and Yorkshire and the Humber in Britain. This snow was in the north half of a depression with east winds centred south of England. Several deaths attributed to the cold weather were reported.

During the night of 18–19 December, five Eurostar trains were stuck in the Channel Tunnel, trapping more than 2,000 people for up to 16 hours after the vehicles suffered electrical failures because of freezing overnight temperatures. Passengers were without heating, lighting and air-conditioning for several hours while food and water ran out. Some passengers were evacuated via service tunnels to car trains, while others were kept on their trains until the trains could be towed out. Eurostar added special services on the evening of 19 December to transport "vulnerable passengers" between London, Paris and Brussels. However, a service from Paris became the sixth train to break down after becoming stuck near Ebbsfleet, Kent. The cause of the breakdowns was unclear; Eurostar initially blamed the sudden contrast between freezing temperatures above ground and the heat of the tunnel, which affected the high-speed engines.

On 19 December, a daily high temperature of -11.5 °C (11.3 °F) was recorded in Mainz, Germany, making it remaining in the two digit negatives all day for the first time since 1956. On the 20th, the December record low of -16.5 °C (2.3 °F) was set with great distance (previously -13.9 °C), and also overall the lowest temperature measured since 1979

On 20 December in the Netherlands, the Royal Dutch Meteorological Institute (KNMI) issued an official weather alarm for the entire country following heavy snowfall () in the west, which eventually spread to the entire country. In most cities bus services were halted and tram service was halted in all four major cities. In northern Italy several locations recorded the lowest temperatures since 1985, with one low reaching −17 °C (1.4 °F).

Police in Poland reported that 15 people froze to death in the country as overnight temperatures fell as low as and 47 people died indirectly as a result of the cold during the month of December. Public appeals were made to the Polish community to report any homeless or drunk people lying outdoors, in an attempt to reduce the number of deaths from exposure to the cold.

In Kosovo, one person died and ten people were injured in traffic accidents because of poor weather conditions. Kosovo Police spokesperson, Arbër Beka, said that one person died in an accident which occurred near Đakovica; there were injuries reported in 16 traffic accidents, and a total of 74 accidents causing property damage. The local police called on residents to be careful on the roads because of the heavy snowfall and very difficult driving conditions."Weather causes problems in Kosovo" B92 20 December 2009. Retrieved 20 December 2009

On 21 December, the M25 motorway and large parts of the M3, M4, M40, M1 and M11 motorways in the United Kingdom were brought to a standstill until late at night and many towns were gridlocked. About 100 people were able to travel from London Victoria Station to Ashford International railway station on a steam train hauled by the locomotive Tornado. Widespread transport disruption affected parts of England, Wales, Scotland and Ireland (except a few southern parts of Munster).

In Bosnia and Herzegovina, three people were found dead from hypothermia in Sarajevo and Teslić."Three people freeze to death in Bosnia" B92 21 December 2009. Retrieved 21 December 2009

22–26 December Fresh overnight snowfall brought renewed problems to parts of the United Kingdom. Particularly badly hit were north Hampshire and the Thames Valley in England. In Basingstoke, some 3,000 motorists were forced to either abandon their vehicles or sleep in them overnight after becoming stuck in gridlocked traffic; approximately 2,000 cars were abandoned. The vehicle recovery service, AA, accused some local authorities of not acting quickly enough to grit the roads, claiming some "key roads" had "not been gritted at all". The Local Government Association dismissed the claims as "unverified, unsubstantiated and unjustified". A man found unconscious in his back garden on the Isle of Lewis, in the Outer Hebrides, after a night out over the weekend died. A homeless charity in France reported that 12 people died during December as a result of the severe cold.

On 23 December, overnight temperatures in the UK once again dropped well below freezing. Dalwhinnie in the central Highlands of Scotland recorded a low of and Edinburgh recorded , causing Scottish Transport Minister Stewart Stevenson to state that conditions on Scottish roads were at their worst in 20 years. Air travel was disrupted in the United Kingdom, with Southampton Airport cancelling (or diverting) all inbound and outbound flights until midday due to a frozen runway. Train services were cancelled for most of the day from Southampton Airport Parkway. A Ryanair flight landing at Prestwick Airport overshot the runway; no injuries were reported and the airport was soon reopened. Two women were killed and more than 40 people injured following a coach crash on an ungritted country road in Cornwall, as a party returned from a trip to see Christmas lights in Mousehole the previous evening. Weather forecasters warned of icy conditions and further snowfall into Christmas Eve, particularly affecting northern England and the East Midlands.

In western Serbia, rapidly melting snow caused the Jadar River in Loznica to flood and resulted in farmland being submerged. Danijela Despotović, of the Hydro-Meteorological Service of Serbia in Loznica, said that the temperature was in the town."Temperature swing causes flooding" B92 23 December 2009. Retrieved 23 December 2009 Heavy snowfall began in Saint Petersburg, Russia. By 26 December the city was under 35 cm of snow, creating the largest December snowfall recorded in the city since 1881.

On Christmas Day, parts of Britain had a White Christmas for the first time since 2004 after snow fell in northern and central Scotland and parts of England (including Nottinghamshire). The Netherlands had its first white Christmas since 1981.

On 26 December (Boxing Day), drivers in Northern Ireland were warned of icy conditions. Conditions in many other parts of the UK continued to improve as milder air moved in from the south. However, northern England and Scotland remained cold and nighttime temperatures continued to drop below freezing. Some Boxing Day sporting fixtures were cancelled (or postponed) because of continuing icy conditions in certain areas, including the National Hunt meeting at Towcester and all but two of the Scottish Football League's matches. Some parts of East Anglia suffered electricity cuts, including Dedham, Stratford St Mary and parts of Colchester; in more remote parts of the region, some were without power for 36 hours.

27–31 December

Parts of England again suffered power cuts on 26–27 December. Scotland experienced fresh snowfall overnight; Perthshire being the most-affected area, where between fell. Temperatures fell to in Tyndrum overnight on 27–28 December, and to at Tulloch Bridge in the Highlands. The Met Office issued fresh severe weather warnings and motorists were advised to drive with caution. The A75 between Stranraer and Newton Stewart was closed due to icy conditions; while the southbound carriageway of the A9 was blocked between the A824 and B8081 in Perth and Kinross following an accident at Gleneagles.

Temperatures dropped to in parts of the Highlands overnight on 28–29 December, with Braemar recording Britain's lowest temperature of the Winter. Fresh travel warnings were issued on 29 December, as wintry conditions continued to cause problems on Scotland's roads. The runway of Inverness Airport was briefly closed because of snow and ice, and First ScotRail reduced its service to and from Glasgow Central because of the severe conditions. However, the snow and icy conditions were good for the Scottish ski industry, which said the weather helped it to experience its best start to the season for several years. Warnings of heavy snow were issued for Wales, the Midlands, Yorkshire and Humber, north-west England, eastern and southern England. More snow began falling across parts of Wales/central and northern England on the evening of 29 December, with Wales recording the heaviest of the snow showers; some rural areas recording up to . Snow was also reported in parts of the West Midlands region and Yorkshire.

On 30 December, Sportscotland Avalanche Information Service (SAIS) issued warnings about conditions on Scottish mountains. However, three people died in three large avalanches. Two climbers were killed as a result of a snow slide on Ben Nevis, while a man was airlifted from Liathach (a mountain in Torridon) after getting into trouble, but died in hospital.

Continued icy weather in Scotland on New Year's Eve led to the cancellation of Hogmanay celebrations in Inverness, amid concerns over public safety; New Year celebrations in other parts of Scotland went ahead as planned. Northeast Scotland experienced fresh snowfall during the afternoon and evening of 31 December. For a second time that week Inverness Airport was closed, forcing several hundred passengers to make alternative arrangements. In Batley, West Yorkshire, 2,500 gallons of water leaked into the local gas network; 400 homes in Dewsbury and Batley were without gas during subzero temperatures. The final homes were reconnected on 7 January. There was also heavy snowfall in Dublin, Ireland, leading to the closure of Dublin Airport for several hours disrupting flights. In Dublin, the snow began 10 minutes before the New Year's Eve countdown.

January 2010

1–5 January