Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weather history. They are defined as lying in the most unusual ten percent (10th or 90th percentile of a probability density function). The main types of extreme weather include heat waves, cold waves and heavy precipitation or storm events, such as tropical cyclones. The effects of extreme weather events are economic costs, loss of human lives, droughts, floods, landslides. Severe weather is a particular type of extreme weather which poses risks to life and property.
Climate change is increasing the periodicity and intensity of some extreme weather events. Confidence in the attribution of extreme weather and other events to anthropogenic climate change is highest in changes in frequency or magnitude of extreme heat and cold events with some confidence in increases in heavy precipitation and increases in the intensity of droughts. Current evidence and climate models show that an increasing global temperature will intensify extreme weather events around the globe, thereby amplifying human loss, damages and economic costs, and ecosystem destruction.
Extreme weather has significant impacts on human society as well as natural ecosystems. For example, a global insurer Munich Re estimates that natural disasters cause more than $90 in billion global direct losses in 2015. Some human activities can exacerbate the effects, for example poor urban planning, wetland destruction, and building homes along floodplains.
Total winter precipitation in the United States had increased by 10 percent since 1900 and that "extreme precipitation events" -- rainstorms that dumped more than two inches of water in twenty-four hours and blizzards -- had increased by 20 percent.
Global warming models indicate that rising global temperatures are likely to affect many atmospheric parameters including precipitation and wind velocity, and raise the incidence of extreme weather events, including storms and heavy rainfall, cyclones and drought. It may or may not be just coincidence that the Munich Reinsurance Company recorded more than 700 'large loss events' in 1998, compared with between 530 and 600 during previous recent years. The most frequent natural catastrophes were windstorms (240) and floods (170), which accounted for 85 per cent of the total economic losses (Munich Re 1998).