have a nearly thankless job. If they predict sunny weather and a storm pops
up, people complain. If they predict a storm and the weather stays calm, people
Since weather conditions affect everything from games to crops, the weather is a constant topic of conversation. And people are almost always worried about it. Why is it so difficult to accurately determine what the weather is going to be?
Location, Location, Location
Iowa is a meeting place for several
weather producing systems. Winds from the Pacific Ocean carry moisture-filled
clouds inland. These clouds bump into the Rocky Mountains. They dump their
contents on the western slopes.
There are no large bodies of water between the Rockies and Iowa. So meteorologists say that Iowa is in the “rain-shadow” of the mountains. This means most of the time the west winds that cross Iowa are dry. And they are hot. Cool, dry air from the north provides relief from summer heat. Or it can make it even colder in the winter. Southerly winds coming up from the Gulf of Mexico provide most of Iowa’s precipitation.
Any of these systems can be in place for a long period of time. They produce stable, sometimes pleasant, sometimes unpleasant weather conditions. Long periods of hot, dry winds from the west can cause drought conditions. A continuous stream of moisture-rich air from the south can cause flooding. When any two of the systems collide, there is a good chance there will be an outbreak of severe weather.
Heat rises. Hot air holds more moisture than cool air. These two facts are the reasons for most of Iowa’s severe weather.
In the summer sunshine heats the
ground. This causes moisture in the soil and in plants to evaporate. The moisture
floats as tiny molecules in the air. If lighter, cooler air moves on top of
warm, heavy air, it keeps the warm, wet air from rising. It cools the water
vapor. In the winter, cooler air that covers Iowa is sometimes met with warm,
moist air. The warm, moist air comes up from the Gulf of Mexico. Summer air
collisions usually make thunderstorms. They can cause tornadoes. Winter weather
collisions make snowstorms. Sometimes they cause blizzards.
Pioneers used many ways to forecast weather. They looked to the sky. They watched animals. They used their senses. Pioneers didn’t have paved roads, tow trucks or early warning systems. They had limited amounts of food and fuel for warmth. Not knowing the weather forecast could be dangerous.
Imagine a pioneer farmer starting a trip to town on horseback on a bright sunny winter day. Suddenly the sun disappears. Snowflakes begin to fall. Soon the ground is covered with snow. The horse struggles through the heavy drifts. The rider’s face is pelted with icy droplets of snow. He wouldn’t have started the trip if he had known about the approaching storm.
Weather can change rapidly. But
climate can stay stable for several thousand years. Climate is the big picture
of the normal weather patterns over a period of many years. Iowa has a “temperate”
climate. There are four distinct seasons.
But this is a big change from the past. How do we know?
Scientists study fossilized pollen and ancient sea creatures. Also, coal deposits and mammoth skeletons tell scientists about past swings in Iowa’s climate. Iowa was located near the equator for hundreds of million years. During that time the climate was tropical. The weather was hot and humid. After the continent moved northward, ice ages brought much cooler weather. The cool weather favored coniferous forests, mastodons and wooly mammoths.
current climate created the tall grass prairie habitat. The air systems coming
up from the Gulf of Mexico brought water to Iowa. There was enough moisture
to help plants grow. But the hot, dry winds from the west discouraged tree growth. Sometimes lightning caused fires. The fires raced across hundreds
of miles before reaching a river.
Trees have most of their bulk and growing points above ground. So, as the fires spread, the trees were destroyed. Prairie grasses and flowers have most of their bulk and growing points below ground. After a fire roared past, they would tap their underground energy stores and sprout again.
The natural plants and animals found
in Iowa have changed over years. They changed because of the weather. Most
mammals grow a thicker coat of fur for winter. They grow a lighter, thinner
coat for the summer. Most birds that feed on bugs and fish leave the state each
winter. Seed eaters can be found in Iowa year round. Many native prairie plants
have hairy leaves. This cuts back the amount of water they lose in the hot
People have learned to adapt as well. Prehistoric cultures that lived at the end of the last ice age and hunted mammoths and mastodons were nomadic, following the animals that provided their food. More recent Indian nations often settled in one area for the growing season, but moved to another location to survive the winter. Since the first wave of Europen settlement, Iowans have tended to stay in one place all year long. Many farmers plant corn, a warm-season grass that grows well in Iowa's climate. Heating and air conditioning can now be found even in tractor and combine cabs, moderating temperature extremes. However, people who don't appreciate the cold winter weather have once again become migratory. They live in the south during the winter, and move back to Iowa in time to enjoy the growing season.
There is no sure way to protect Iowa’s crops and buildings from wind, drought, flood, hail, tornadoes and frost. But people have learned to lessen the losses caused by weather. Early Indian nations settled and farmed on river floodplains. Now these areas are often used as greenspace. When the land is left in its natural state, floodwaters might not destroy houses or crops. And there is less erosion.
Iowa’s Future Weather
Some scientists think that the world
is between ice ages. They think that glaciers will grow and plow across the
land again. Some scientists believe that human activities are causing the
earth to warm. This could eventually cause polar ice caps to melt. Iowa scientists
have only 200 years of records to study. That sounds like a lot. But in a
world that is billions of years old 200 years isn’t much. It’s
not easy for scientists to see changes that can take thousands of years to
Iowans talk about weather. They worry about weather. Meteorologists look to their weather tracking systems. They predict the weather. Sometimes they get it right. Sometimes they don’t. Iowans talk about it either way!
- Iowa Association of Naturalists. Iowa Weather: Iowa Physical Environment Series. Ames, Iowa: ISU Extension Service. 1999.
- Prior, Jean C. Landforms of Iowa. Iowa City, IA: University of Iowa Press, 1991.
- Troeger, Jack Clayton. From Rift to Drift: Iowa’s Story in Stone. Ames, Iowa: Iowa State University Press, 1983.