An increase in heatwaves is almost certain, with heavier rainfall, more floods, stronger cyclones, landslides and more intense droughts, warns the UN.
The Intergovernmental Panel on Climate Change (IPCC) has urged countries to come up with disaster management plans to adapt to the growing risk of extreme weather events linked to human-induced climate change.
The latest report gives differing probabilities for extreme weather events based on future greenhouse gas emissions scenarios, but the thrust is that extreme weather is likely to increase.
"It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes will occur in the 21st century on the global scale," the IPCC report said.
"It is very likely that the length, frequency and/or intensity of warm spells, or heat waves, will increase," it added.
"A one-in-20-year hottest day is likely to become a one-in- two- year event by the end of the 21st century in most regions," under one emissions scenario.
An exception is in very high latitudes, it said. Heatwaves would likely get hotter by "1-3C by mid-21st century and by about 2-5C by late-21st century, depending on region and emissions scenario."
Delegates from nearly 200 countries will meet in South Africa from November 28 for climate talks with the most likely outcome modest steps towards a broader deal to cut greenhouse gas emissions to fight climate change.
The report said tropical cyclones were likely to become less frequent or stay the same, but the ones that do form are expected to be nastier.
The UN, the International Energy Agency and others say global pledges to curb emissions of CO2 and other greenhouse gases are not enough to prevent the planet heating up beyond 2C, a threshold scientists say risks an unstable climate in which weather extremes become more common and food production more difficult.