A key feature common to both events was the orographic enhancement of the rainfall across high ground, with approximately 10 times as much rain (or more) falling in the Lake District fells compared to coastal locations.
This compares against a factor of approximately 3 times for annual average rainfall (3000mm compared to 1000mm).
For a description of monthly summaries, including rainfall statistics from 1910, please refer to the Climate summaries.
For a list of UK weather records, please refer to these Weather extremes.
341.4mm of rain fell at Honister Pass, Cumbria, in 24-hours to 1800 GMT on 5 December 2015, a new UK rainfall record, while at Thirlmere 405.0mm also set a new record for two consecutive rain-days (0900 - 0900 GMT).(The Met Office midas database holds at least 200,000 station-years of daily rainfall data, but the majority of these digitized data are from 1961).The Centre for Ecology and Hydrology (CEH) north west floods hydrological update discusses the rarity of these exceptionally high rainfall totals.The heaviest of the rain eased away slightly from west Cumbria at around 1800 GMT on 5 December, but continued at the other locations slightly further east.The rainfall from this event was remarkable for its duration, rather than intensity, and was notably similar in character to Seathwaite in November 2009.In the Yorkshire Dales, Malham Cove waterfall briefly flowed again for the first time in living memory.Storm Desmond also caused considerable flooding problems elsewhere across parts of County Tyrone, County Fermanagh, and the Republic of Ireland.BBC news - storm Desmond: thousands of people forced out of homes BBC news - storm Desmond: floods across large parts of Scotland The analysis chart for 1200 GMT on 5 December shows a deep Atlantic low pressure system to the east of Iceland, with associated fronts stretching across northern Britain.The UK was located in a mild, moist south-westerly airstream with these fronts bringing exceptionally prolonged and heavy rainfall as the air was forced to rise across high ground.There were two fatalities and many road and rail links were cut, including the West Coast Main Line.Schools and hospitals were closed in the flood affected areas.