Higher temperatures could see up to 5,900 more people dying as a result of hot summers, but thousands of cold-related deaths - between 3,900 and 24,000 - are likely to be avoided in winter by the 2050s, the research shows.
The costs to the UK of flooding could rise to billions of pounds a year in the coming decades, according to the first national assessment of the risks of climate change.
The UK will also face threats including water shortages, more droughts and diseases such as red band needle blight which could hit the timber industry in the next century, the assessment conducted for the Government showed.
However the changing climate will bring some opportunities to the UK, including the chance to grow new crops and even the possibility of more tourism as temperatures get milder.
The study looked at the implications of the kind of changes the UK is likely to see to its weather, from hotter summers to more extreme weather events.
Threats were assessed against three scenarios for potential climate change, ranging from low temperature rises if significant cuts are made to emissions to large rises if little action is taken - the trajectory the world is currently on.
It estimated the magnitude of each threat and how that might change over the coming century, and also the confidence in the assessment based on the amount of evidence available.
The report will feed into a national programme to adapt to climate change - some of which is already inevitable - which will be published next year.
The existing climate already makes the UK vulnerable to extreme weather, such as the 2007 summer floods which cost £3 billion in England alone.
The £2.8 million project, a legal requirement under the Climate Change Act, revealed the high risk flooding poses, with the costs of floods potentially rising from current levels of £1.2 billion a year to between £1.5 billion and £3.5 billion by the 2020s, and £2.1 billion to £12 billion by the 2080s for England and Wales.
Insurance and the provision of mortgages could come under threat from more frequent floods, while the risk of significant flooding to homes and even people's mental health will be an increasingly serious issue.
Other risks include increasing demand for irrigation of crops, more invasive species, damage to nature, the loss of agricultural land to coastal erosion, and a loss of staff hours due to overheated office buildings.
Environment Secretary Caroline Spelman said: "This world class research provides the most comprehensive case yet on why we need to take action to adapt the UK and our economy to the impacts of climate change.
"It shows what life would be like if we stopped our preparations now, and the consequences such a decision would mean for our economic stability."
She said the assessment would be vital in understanding what needed to be done to stop potential threats becoming a reality, and provided opportunities for British firms to develop innovative products and services to tackle the risks.
Lord Krebs, chairman of the group which advises the Government on adapting to climate change, said: "Without an effective plan to prepare for the risks from climate change the country may sleep walk into disaster.
"This report represents an important step in the process and demonstrates why the UK needs to take action to adapt now."
Responding to the report, the Government outlined existing policies it already has in place to tackle present and future climate issues, including £2.1 billion spending on flood defences and coastal erosion over the next four years, although it has reduced spending on flooding, and the England heatwave plan.
In addition to setting out the impacts of climate change on the UK, the report warns the threats will be greater in other parts of the world, with implications here for supply chains, migration and international political stability.
But there could also be some opportunities for British businesses to provide services such as insurance to other countries.
Climate change charities said that the report demonstrated the serious impact climate change will make on the UK, but said that the government should not forget the harsher impact it will make on the developing world.
Dr Doug Parr Chief Scientist at Greenpeace said:
“This report demonstrates that not only will Britain’s infrastructure and wildlife be impacted by climate change, but we will feel the consequences of political and economic of instability in other parts of the world.
"Whilst we must now plan to be more resilient, UK must also keep pushing the EU and international processes to deliver the emissions cuts that will limit the long-term consequences”.
The top risks include:
- Flooding costs could rise from the current £1.2 billion a year to between £2.1 billion and £12 billion a year by the 2080s.
- People hit by storms and floods may suffer mental health problems such as depression.
- Water shortages could increase, with a potential deficit of between 773 and 2,570 million litres of water a day in the Thames river.
- Farmers could experience crop losses due to flooding and the forestry industry could see timber yield and quality reduced by drier weather.
- Timber production could be hit by the spread of pests and diseases such as red band needle blight.
- Rising sea levels could hit natural assets such as beaches and buildings including tourist attractions and historical monuments, with knock-on impacts for businesses that rely on them.
- Higher temperatures could see around 580 to 5,900 more people dying as a result of hot summers and heatwaves by the 2050s.
- The number of days a year when temperatures rise above 26C is predicted to increase from 18 in London to between 27 and 121 in the 2080s.
- Hot days will see buildings too hot to work in and a greater demand for air conditioning. But between 3,900 and 24,000 cold-related deaths could be avoided in winter by the 2050s.
- Increased summer temperatures could also lead to heat-related damage and disruption to energy networks and transport infrastructure, such as buckling of rail tracks.
- Increased subsidence and landslips could hit transport and buildings, and milder winters may reduce cold weather-related damage, delays and disruption.
- Fish species could shift north, reducing the UK's cod fishery but potentially increasing plaice stocks. Invasive species could also spread north within the UK.
- Native species, particularly those which depend on special habitats rather than the general countryside, may struggle to move to keep up with a changing climate, while wildlife and habitats are likely to be at increasing risk from drier soils.
- Wildfires are likely to become more of a serious issue.
- The melting of Arctic ice could open up new container shipping routes through the region, improving trade links with Asia and the Pacific.