Charles
V. Schwab and Laura
Miller
Iowa State University Extension
- Tornado-like
winds pick up a storage shed and two farm workers are hurt.
- Caught
in a sudden summer thunderstorm, a tractor operator is seriously
burned after being struck by lightning.
- A
truck stalls near an isolated livestock facility and the
driver is hospitalized after walking two miles in severe
cold to get help.
- Two
farm workers suffer heat stroke while baling hay on an hot,
humid afternoon.
Farmers
work in all kinds of weather. These examples of injuries caused
by severe weather can and do happen every year in agricultural
operations. While they cannot avoid the elements altogether,
farmers must know when to take cover and the type of precautions
necessary to avoid serious injuries or death.
This
publication briefly reviews weather conditions that can play
havoc with Iowans - tornadoes, thunderstorms, winter storms,
and excessive heat - and special considerations for farm workers.
Every
year, between 600 and 1,400 tornadoes are reported in the United
States that result in as many as 400 deaths and more than 1,500
injuries. One of the worst years in recent history was 1974,
when early spring tornadoes killed 315 people in the Midwest
and the South.
Tornadoes
are small but violent storms that can pack up to 250 mph winds
and travel 50 miles. One weather system can spawn multiple
storms. For example, the Plains Outbreak, April 26-27, 1991,
produced more than 70 tornadoes that caused 21 deaths, 308
injuries and more than $277 million damage. In Iowa, most
tornadoes occur from April to June between noon and midnight,
although they can occur at any time of the year and at any
time of the day or night.
What
to watch for:
- dark,
often greenish sky,
- large
hail,
- a
cloud that looks like a wall, and
- a
loud roar, similar to a freight train.
What
to do:
- In
an open field, stop and get out of the tractor or vehicle.
Lie in a low area or ditch away from the tractor. Cover
your head with your arms to protect yourself from flying
debris.
- Do
not try to outrun a tornado on your tractor. A tornado's
speed and direction are deceptive.
- Know
which buildings can offer the best protection, such as a
building with a below-grade floor (basement), or a building
with a strong inner structure (barn). Stay away from the
outside walls of the building.
Table
1. Wind Chill Factor Comparisons (°F) |
Air
temp. (°F)
|
|
Wind
speed (miles per hour)
|
Calm
| 15
| 30
| 40
|
30 |
30 |
11 |
-2 |
-4 |
20 |
20 |
-6 |
-18 |
-22 |
10 |
10 |
-18 |
-33 |
-36 |
0 |
0 |
-33 |
-49 |
-54 |
-10 |
-10 |
-45 |
-63 |
-69 |
-20 |
-20 |
-60 |
-78 |
-87 |
NOTE:
Wind speeds greater than 40 mph have little additional
chilling effect. Source: Stalled...but Safe, NCR
Extension Publication 170. |
Blizzards
and periods of extreme cold are a fact of life in Iowa. Although
many people heed winter storm warnings, stay off roads, and
remain indoors, these storms can be deadly. In 1993, a severe
snowstorm hit the Eastern United States and killed 270 people.
Each year, 43 deaths are attributed to winter storms in the
United States.
To alert
people to the dangers, the National Weather Service issues
winter storm watches and warnings. Wind chill indicates how
cold it really feels by combining air temperature with wind
speed.
In addition
to exposure, cold weather also presents risk of hypothermia.
This serious medical condition develops when the core body
temperature drops below 96°F. Most susceptible are elderly
persons (due to inactivity and low metabolism) and children
(lack of insulating body fat). However, other people can develop
hypothermia even in relatively mild conditions if they're
not dressed for the weather, they get wet, or are caught in
a sudden, strong wind. Alcohol consumption, chronic illness,
and certain medications also can decrease body temperature.
Severe
hypothermia can lead to serious problems, and the person can
go into shock. Emergency medical treatment is recommended.
Table
2. Heat Index (Apparent Temperature) |
Air
temp. (°F) |
Relative
Humidity (percentage) |
0 |
10 |
20 |
30 |
40 |
50 |
60 |
70 |
80 |
85 |
90 |
95 |
100 |
140 |
125 |
|
|
|
|
|
|
|
|
|
|
|
|
135 |
120 |
|
|
|
|
|
|
|
|
|
|
|
|
130 |
117 |
131 |
|
|
|
|
|
|
|
|
|
|
|
125 |
111 |
123 |
141 |
|
|
|
|
|
|
|
|
|
|
120 |
107 |
116 |
130 |
148 |
|
|
|
|
|
|
|
|
|
115 |
103 |
111 |
120 |
135 |
151 |
|
|
|
|
|
|
|
|
110 |
99 |
105 |
112 |
123 |
137 |
150 |
|
|
|
|
|
|
|
105 |
95 |
100 |
105 |
113 |
123 |
135 |
149 |
|
|
|
|
|
|
100 |
91 |
95 |
99 |
104 |
110 |
120 |
132 |
144 |
|
|
|
|
|
95 |
87 |
90 |
93 |
96 |
101 |
107 |
114 |
124 |
136 |
|
|
|
|
90 |
83 |
85 |
87 |
90 |
93 |
96 |
100 |
106 |
113 |
117 |
122 |
|
|
85 |
78 |
80 |
82 |
84 |
86 |
88 |
90 |
93 |
97 |
99 |
102 |
105 |
108 |
80 |
73 |
75 |
77 |
78 |
79 |
81 |
82 |
85 |
86 |
87 |
88 |
89 |
91 |
75 |
69 |
70 |
72 |
73 |
74 |
75 |
76 |
77 |
78 |
78 |
79 |
79 |
80 |
70 |
64 |
65 |
66 |
67 |
68 |
69 |
70 |
70 |
71 |
71 |
71 |
71 |
72 |
NOTE:
People with weight, or alcohol problems, elderly persons,
young children, and those on certain medications) are
at high risk for heat disorders. When the Heat Index reaches
90°, sunstrokes, heat cramps and heat exhaustion are
possible during prolonged exposure and/or physical activity.
Source: 1979 Journal of Applied Meteorology 18:861-873. |
What
to watch for:
- signs
of hypothermia, including confusion, clumsiness, drowsiness,
slurred speech, shallow breathing, and uncontrollable shivering;
- signs
of frostbite, including numbness in the extremities (ear
lobes, nose, cheeks, fingers, toes, hands, and feet);
- winter
storm warnings; and
- a
low wind chill temperature.
What
to do:
- Avoid
outdoor work during winter storms and severe cold.
- Dress
in layers. Cotton socks worn under two pairs of wool socks
and heavy, properly fitting boots can keep feet warm.
- Cover
all exposed areas, including neck, face, fingers, and wrists.
- Always
wear a hat.
- Keep
extra clothes, a blanket, source of emergency heat, and
flares in all vehicles.
In
a normal year, an average of 175 people succumb to the demands
of summer heat. Heat cramps, heat exhaustion, and heat stroke
are real risks for people exposed to excessive heat. In the
disastrous heat wave of 1980, more than 1,250 people died.
Heat
disorders occur when the body is unable to either shed heat
by sweating, or make up fluids (or salt) lost through perspiration.
The most serious condition, heat stroke, requires emergency
medical treatment and can be fatal. The severity of heat disorders
tends to increase with age and physical activity. Persons
with weight or alcohol problems are more susceptible to heat
reactions. Exposure to full sunlight and humid conditions
add to how hot it really feels. Strong, very hot, dry winds
also increase the risk of developing heat disorders.
What
to watch for:
- the
daily Heat Index (HI) from the National Weather Service,
a combination of air temperature and relative humidity.
- symptoms
of heat disorders including painful muscle spasms (heat
cramps), heavy sweating, weakness, cold and clammy skin,
fainting, or vomiting (heat exhaustion), and hot dry skin,
rapid pulse, and high body temperature (heat stroke).
What
to do:
- Reschedule
strenuous activity to coolest time of day.
- Wear
light-colored clothing that reflects heat.
- Drink
plenty of water before you feel thirsty.
- Always
wear a wide-brimmed hat to shield face and neck from sun.
Use sunscreen.
- Take
frequent breaks in the shade, or a long break in an air-conditioned
room. Guard against drastic changes over long periods of
time by keeping the air conditioner at a moderate, rather
than chilly, setting.
Compared
to other storms, thunderstorms are small. They typically are
only 30 miles wide and last an average of 30 minutes. Despite
their size, thunderstorms are more deadly than tornadoes. All
thunderstorms produce lightning, which kills an average of 93
people every year. Some thunderstorms produce heavy rain that
leads to flash flooding, which kills approximately 140 people
every year. Of the estimated 100,000 thunderstorms each year
in the United States, only 10 percent are classified as severe.
Most
deaths by lightning happen outdoors, although you can be injured
from lightning while indoors (e.g., talking on the telephone,
taking a shower or bath, or standing near a window or open
door). The air near a lightning strike is heated to 50,000°F,
hotter than the surface of the sun. To estimate the distance
in miles between you and the lightning flash, count the seconds
between the lightning and thunder and divide by five.
Contrary
to popular belief, lightning often strikes areas outside of
heavy rain and may occur as far as 10 miles away from any
rainfall. Many people also believe that "heat lightning" after
very hot summer days poses no threat. In reality, "heat lightning"
is from a storm too far away for the thunder to be heard.
Caution is advised because the storm could be moving toward
you.
Flash
flooding quickly can result in fatalities when preventative
actions are not taken, such as avoiding low-water bridges
or roads that could be washed out. Many deaths occur when
people are trapped in vehicles. When a storm occurs at night,
the warning may not reach people who need to move out of or
avoid low-lying areas.
What
to watch for:
- increasing
wind,
- flashes
of lightning,
- sound
of thunder, and
- static
on your AM radio.
What
to do:
- In
an open field, find a low spot away from trees, fences,
and poles. Make sure the place is not subject to flooding.
- If
you are in the woods, take shelter under shorter trees.
- If
you have no shelter, make yourself the smallest target by
squatting low to the ground on the balls of your feet. Minimize
contact with the ground, and place your hands on your knees
with your head between them when your skin tingles or your
hair stands on end.
- If
you are in a tractor or other vehicle during an electrical
storm, stay put. Vehicles often provide better protection
than lying exposed in open fields.
- When
a flash flood warning has been issued for your area, avoid
low-lying areas, and do not drive over low-water bridges,
small creeks, or roads that may be soft or partially washed
out. It is better to spend the extra time to take other
routes than to be caught in swiftly moving floodwaters.
The
National Weather Service issues daily forecasts and long-range
weather outlooks, and decides when to issue severe weather watches.
Private companies also issue forecasts that help farmers plan
field work and monitor market prices.
Severe
weather watch:
Indicates
when conditions are favorable for the development of severe
weather, such as tornadoes, thunderstorms, and blizzards.
Severe
weather warning:
Indicates
when a tornado, severe thunderstorm, or winter storm is in the
immediate vicinity. People who are outdoors should take appropriate
actions as soon as possible.
A
National Oceanic and Atmospheric Administration (NOAA) radio
provides more accurate and current weather information that
is specific to your area. Some NOAA radios have a feature that
automatically sounds a tone when a watch or warning is issued
in your area.
How
much do you know?
- When
a tornado warning is issued you should:
- watch
the weather closely.
- take
shelter.
- wait
until you hear further instructions.
- Lightning
occurs only where it is raining. True or false?
- Hypothermia
is:
- a
disease of the hypothalamus gland.
- not
a concern in the summer months.
- a
condition marked by low body temperature.
- a
condition that stops when you go indoors.
- The
Heat Index (HI) measures how hot it really feels by combining
the actual air temperature with the relative humidity. True
or false?
- Wind
chill combines wind speed and air temperature to indicate
how cold it really feels. True or false?
See
answers at the end of the next section.
What
can you do?
Being prepared
can help farmers respond to all kinds of weather. Follow these
tips to make sure you're safe while working outdoors:
- Check
weather reports before planning work activities.
- Make
sure you have a way of receiving weather information while
you work, especially at remote locations.
- Prepare
a family response plan for all types of severe weather conditions.
- Enroll
in a first aid course.
Answers
to quiz:
1-b;
2-False; 3-c; 4-True; 5-True.
This
publication provides only the basics about severe weather and
related medical conditions, and is not intended to be a first
aid guide. For more information, enroll in a first aid course
or consult a first aid manual. If you or someone else experiences
any of the symptoms described in this publication, get emergency
medical treatment as soon as possible.
More
information about severe storms also is available from the
American Red Cross, which participates in production of various
preparedness guides issued by the U.S. Department of Commerce
and the National Weather Service. County health departments
also may have materials about planning for weather emergencies.
Related
publications:
Also available
at any ISU extension office are these Safe Farm publications:
- Farm
emergency and first aid kits, Pm-1563k
- How
to respond to farm accidents, Pm-1518l
- Remember
sun safety in the field, Pm-1518h
Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
This document
is Fact Sheet
Pm-1563
i
,
a series of the Safe Farm Program, Iowa State University Extension,
Ames, Iowa. Safe Farm promotes health and safety in agriculture.
It is funded by the National Institute for Occupational Safety
and Health (NIOSH #U05/CCU706051-03), Iowa State University,
and a network of groups that serve Iowa farm workers and their
families. Publication date: December 1994.
Prepared
by Charles V. Schwab, extension farm safety specialist, and
Laura Miller, extension communications, Iowa State University
Extension. Reviewed by S. Elwynn Taylor, extension climatologist.
|