A series of low pressure systems steered by the jet stream brought the wettest April in 100 years, and flooding across Britain and Ireland.

Continuing through May and leading to the wettest beginning to June in 150 years, with flooding and extreme events occurring periodically throughout Britain and parts of Atlantic Europe.

[4] 3 June saw the Thames Diamond Jubilee Pageant beleaguered by heavy rain, 46 people from the boats were treated for the effects of the cold weather, and six were taken to hospital with symptoms of hypothermia.

10–11 June saw a small but active area of low pressure track slowly east through the English Channel, eventually becoming slow moving for almost 24 hours near the Sussex coast.

Two inches of overnight rain from back building thunderstorms caused flash flooding, damaging properties and leaving 1,000 homes without power for several hours.

[12] The following day the Northern Ireland Fire and Rescue Service said that it had dealt with 700 flood-related calls, while Finance Minister Sammy Wilson announced that those affected by the floods would be eligible to apply for up to £1,000 in emergency funding.

[13] On the morning of 28 June, supercell thunderstorms developed over Wales shortly after 8.00 a.m., then moved separately across England to the Midlands and the north, leaving a trail of disruption in their wake.

[14] Hailstones as large as golf balls fell in parts of the East Midlands, while the 2012 Olympic torch relay was briefly halted by lightning.

[14] Another supercell storm struck Tyneside without warning at the height of the evening rush hour causing widespread damage and travel chaos, locally known as the Toon Monsoon.

Northern Powergrid reported that 23,000 properties were left without electricity in North-East England after flash flooding and lightning storms hit the area.

South Yorkshire experienced heavy rainfall, and 52 people were evacuated from a care home in Thurnscoe due to a flood warning being issued in the area.

An emergency command centre was set up by South Yorkshire Police in Sheffield over fears of flooding in the city, and authorities advised people to avoid the Meadowhall area because of high water levels on the River Don.

The South West of England also suffered from river & surface flooding, and the Met Office placed the region on a red warning for severe weather.

[23] Officials at Silverstone Circuit on the Northamptonshire/Buckinghamshire border had to turn away thousands of fans attending the Formula 1 Grand Prix qualifying sessions on Saturday 7 July due to heavy rainfall the previous day.

A cursory inspection of the landslip did not reveal the presence of the vehicle and it was not until after the couple were reported as missing that the police re-investigated the debris and found the crushed car on 15 July.

[27] 4–5 August saw localised flooding across the UK in Devon, Tyne and Wear, West Yorkshire and Southern Scotland from torrential rains, in places exceeding 30 mm over a short time.

[34] 11 October brought flooding to the Devon village of Clovelly following 5 cm (2 in) of rainfall, a torrent of water cascaded down the steep cobbled main street to the harbour.

On 22 November a man died after his car was washed down a flooded brook in Chew Stoke, Somerset and trapped against a small bridge.

[49] Around 500 houses were flooded, RNLI lifeboats evacuated residents and an elderly woman was found dead in her own property after the River Elwy swelled to 6 ft above its normal level in the town of St Asaph in North Wales on 27 November.

[56][57] On 19 December a front from the low Petra brought rainfall, and the following day the Environment Agency ordered the evacuation of the village of Wallington, Hampshire, after fears that cracks in the flood wall could indicate potential failure.

[58] A series of weather fronts associated with low pressure areas brought flooding to Helston in Cornwall and Braunton in Devon on the night of 21 December.

[59] Multiple landslips occurred in Swanage Dorset, which were caught on camera by the local coastguard,[60] who produced a map of slips and beach closures in the area.

In April, the wave pattern underwent a significant shift to bring the UK under the influence of strong low pressure, with prevailing south-westerly flow and heavy rainfall.

[73] 28 June 2012 supercells in the United Kingdom and Belgium brought intense heavy rain which caused flash flooding and further saturated the ground water levels.

[74][75][76] Factors involved in the extreme storms of summer 2012 were the relatively high sea-surface temperature in the Atlantic Ocean west of the UK, which increased moisture content of the air as it passed over it and secondly, the persistence of an upper trough (a low pressure in the higher atmosphere) helping the development of strong convection.

[79] November to April is generally the wetter half of the year in the British Isles, which means heavy or prolonged winter rainfall presents a heightened risk of flooding as soils and aquifers are already saturated.

[86] The UK government announced on 30 November that £120 million of new funding would be released to speed up building of 50 flood defences by Defra,[87] which would prioritize schemes in Leeds city centre, Sheffield, Exeter, Derby and Ipswich.

[88] Anne McIntosh MP for Thirsk and Malton and vice-president of the Association of Drainage Authorities questioned whether the government had prioritized the right schemes in their announced package of new funding.

Noting that the Pitt Review of the UK floods of 2007 demanded that Government prove rivers are being dredged regularly, she raised the issue of whether this could be maintained as the maintenance spend of the Environment Agency was being cut.

The BGS team mapped a large concentration of landslips in the southwest of England, a region frequently experiencing flooding during the year,[103] showing a correlation of landslides and rainfall anomaly during 2012.