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Extreme Weather Event
Article by: Theodore G. Shepherd, Department of Meteorology, University of Reading, Reading, United Kingdom.
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Any weather event that is unusual for
a particular location or severe in its ef-
fects. The most commonly considered ex-
amples of extreme weather events include
heat waves, cold snaps, heavy rainfall or
snowfall, ice or hail storms, droughts, ex-
tratropical or tropical cyclones (hurricanes;
Fig. 1), storm surges, and tornadoes.
Extreme weather events arise by chance
from favorable atmospheric conditions.
Some develop rapidly and their effects
are intense but short-lived. Others are
slow-onset events and the severity of their
effects comes from their persistence over
time. In recent years, the economic losses
from extreme weather events have regu-
larly exceeded U.S. $100 billion per year.
Forecasting of extreme weather events is,
naturally, a major focus of weather predic-
tion, but there is also increasing interest in
the effects of climate change on extreme
weather events.
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Key Concepts
• In general, there is no unique definition of an extreme weather event; what is considered "extreme" depends
on the local context.
• The most common extreme weather events are heat waves, cold snaps, heavy precipitation, ice or hail storms, droughts,
hurricanes, storm surges, and tornadoes.
• A main motivation for weather forecasting is to predict extreme weather events before they occur, so as to issue
warnings and minimize damage to life and property.
• Climate change can be expected to alter the magnitude and frequency of extreme weather events. The scientific
understanding of the nature and extent of these changes relies on understanding thermodynamic and dynamic aspects
of the event type, and there is high uncertainty in the latter.
• The role of climate change in any given extreme event, called extreme event attribution, varies greatly among different
event types, and is a rapidly evolving area of scientific research.
Fig. 1: Satellite image showing the rare occurrence of three Atlantic tropical cyclones (known as hurricanes) at the same
time: Irma, José, and Katia, on September 9, 2017.
(Credit: NOAA-NASA-GOES)
