Hazards which originate above the surface of the earth (in the atmosphere) are called exogenous hazards.

1. HEAT WAVES

2. HEAT WAVES
• A Heat Wave is a period of abnormally high
temperatures, more than the maximum temperature
that occurs during the summer season.
• Heat Waves typically occur between March and
June, and in some rare cases even extend till July.
• The extreme temperatures and resultant
atmospheric conditions adversely affect people
living in these regions as they cause physiological
stress, sometimes resulting in death.

3. CRITERIA’S FOR HEAT WAVES
The Indian Meteorological Department (IMD) has
given the following criteria for Heat Waves:
• Heat Wave need not be considered till maximum
temperature of a station reaches atleast 40 degrees
centigrade's for Plains and atleast 30 degrees
centigrade's for Hilly regions.
• When maximum temperature of a station is more
than 40*C Heat Wave Departure from normal is
4*C to 5*C Severe.

4. Contd…
• When actual maximum temperature remains 45*C
or more irrespective of normal maximum
temperature, heat waves should be declared.
• India is also feeling the impact of climate change in
terms of increased instances of heat waves which
are more intense in nature with each passing year,
and have a devastating impact on human health
thereby increasing the number of heat wave
casualties.

5. Health Impacts of Heat Waves
• The health impacts of Heat Waves typically
involve dehydration, heat cramps, heat exhaustion
and/or heat stroke. The signs and symptoms are as
follows:
• Heat Cramps: A type of heat illness, are muscle
spasms that result from loss of large amount of salt
and water through exercise. Heat cramps are
associated with cramping in the abdomen, these
were accompanied with fever below 39*C
i.e.102*F.

7. Heat Exhaustion
• Heat exhaustion is a condition whose
symptoms may include heavy sweating,
heavy pulse rate, weakness, headache,
vomiting, muscle cramps and sweating.

8. Heat Stoke
• A condition marked by fever and often by
unconsciousness, caused by failure of the
body's temperature-regulating mechanism
when exposed to excessively high
temperatures.

10. RECOVER AND BUILD
• If you think someone is suffering from the heat:
• Move the person to a cool place under the shade
• Give water or a rehydrating drink
• Consult a doctor if symptoms get worse or are long
lasting or the person is unconscious
• Cool the person by putting a cool wet cloth on
his/her face/body

11. COLD WAVES

12. COLD WAVES
• A cold wave (also known as a cold snap or
cold spell) is a weather phenomenon that is
distinguished by a cooling of the air.
Specifically, the U.S. National Weather
Service, a cold wave is a rapid fall in
temperature within a 24-hour period
requiring substantially increased protection
to agriculture, industry, commerce, and
social activities.

13. Contd…
• In the some countries, a cold spell is defined
as the national average high temperature
dropping below 20 °F (−7 °C). A cold wave
of sufficient magnitude and duration may be
classified as a cold air outbreak (CAO).
• This minimum temperature is dependent on
the geographical region and time of year.

14. EFFECTS
• A cold wave can cause death and injury to
livestock and wildlife.
• Exposure to cold mandates greater impact on
intake for all animals, including humans, and if a
cold wave is accompanied by heavy and persistent
snow, grazing animals may be unable to reach
needed food and die of hypothermia.
• They often necessitate the purchase of foodstuffs to
feed livestock at considerable cost to farmers.

15. EFFECTS
• Extreme cold waves often causes poorly insulated
water pipelines and leads to freeze.
• Even some poorly protected indoor plumbing
ruptures as water expands within them, causing
much damage to property and costly insurance
claims.
• Cold waves that bring unexpected freezes and
frosts during the growing season in mid-latitude
zones can kill plants during the early and most
vulnerable stages of growth, resulting in crop
failure as plants are killed before they can be
harvested economically.