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# WEATHER

## How do I convert Fahrenheit to Celsius to Kelvin?

Fahrenheit and Celsius are two common temperature scales used throughout the world. Temperature in Fahrenheit can be converted to Celsius by subtracting 32 and multiplying by five; divide that number by nine and you have Celsius. Conversely, you can convert Celsius to Fahrenheit by adding 32, multiplying by nine and finally dividing by five. Kelvin, a system used by scientists, is based on the same scale as Celsius. All you have to do is add 273 to your Celsius temperature to obtain Kelvin. Zero degrees Kelvin is negative 273° Celsius.

## What is a low high temperature and a high low temperature?

When meteorologists look at daily temperature, there is always a low and a high temperature for each day. If the high temperature is the coldest high temperature for that day or for the month, you have a new record—a new low high. Conversely, if the low temperature for a day is quite warm and breaks records, that's a new high low!

## What are some world weather records?

The following are some amazing weather records. The wettest: Cherranpunji, India, with 500 inches (1,270 centimeters) of rainfall per year; the coldest: Antarctica, with a measurement of -129° Fahrenheit (-89.4° Celsius); the driest: Arica, Chile, which only receives 0.004 inches (0.01 centimeters) of rainfall per year; and the hottest: Azizia, Libya, which has sizzled at 136° Fahrenheit (57.7° Celsius).

## What world weather records does the United States hold?

The United States claims the world's highest surface wind (231 miles [372 kilometers] per hour peak gust in New Hampshire), world's greatest average yearly precipitation (472 inches [1,200 centimeters] in Hawaii), and the world's heaviest 42-minute rainfall (12 inches [31 centimeters] in Missouri).

Why are there so many discrepancies in the world records of weather?

The discrepancies in the data reflect the length of time that we use to measure weather phenomena. Some records were set by observing the weather over decades; others only occurred during the span of a few years or months, or even hours or minutes.

## Why is it more likely to rain in a city during the week than on the weekend?

Urban areas have an increased likelihood of precipitation during the work week because intense activity from factories and vehicles produce particles that allow moisture in the atmosphere to form raindrops. These same culprits also produce warm air that rises to create precipitation. A study of the city of Paris found that precipitation increased throughout the week and dropped sharply on Saturday and Sunday.

## What does a 40 percent chance of rain really mean?

When the morning weather report speaks of a 40 percent chance of rain, it means that throughout the area (usually the metropolitan area) there is a 4 in 10 chance that at least 0.001 of an inch of rain (0.0025 centimeters) will fall on any given point in the area.

## Why is it hotter in the city than in the countryside?

Cities have higher temperatures due to an effect known as the urban heat island. The extensive pavement, buildings, machinery, pollution from automobiles, and other things urban cause this warmth in the city. Cities such as Los Angeles can be up to five degrees hotter than surrounding areas due to the urban heat island effect. The term comes from temperature maps of cities where the hotter, urban areas look like islands when isotherms (lines of equal temperature) are drawn.

## What is a thunderstorm?

Thunderstorms are localized atmospheric phenomena that produce heavy rain, thunder and lightning, and sometimes hail. They are formed in cumulonimbus clouds (big and bulbous) that rise many miles into the sky. Most of the southeastern United States has over 40 days of thunderstorm activity each year, and there are about 100,000 thunderstorms across the country annually. Thunderstorms are different from typical rainstorms because of their lightning, thunder, and occasional hail.

## What is air pollution?

Air pollution is caused by many sources. There are natural pollutants that have been around as long as the Earth, such as dust, smoke, volcanic ash, and pollens. Humans have added to air pollution with chemicals and particulates due to combustion and industrial activity.

# WIND

## Where does wind come from?

The Earth's atmospheric pressure varies at different places and times. Wind is simply caused by the movement of air from areas of higher pressure to areas of lower pressure. The greater the difference in pressure, the faster the wind blows. Some detailed weather maps show wind speed along with isobars (areas of equal air pressure) indicating the level of air pressure.

## In which direction does the west wind blow?

It blows from the west to the east. Wind is named after the direction from whence it comes.

## What are the westerlies?

These winds flow at mid-latitudes (30 to 60 degrees north and south of the equator) from west to east around the Earth. The high-altitude winds known as the jet stream are also westerlies.

## What are monsoons?

Occurring in southern Asia, monsoons are winds that flow from the ocean to the continent during the summer and from the continent to the ocean in the winter. The winds come from the southwest from April to October, and from the northeast (the opposite direction) from October to April. The summer monsoons bring a great deal of moisture to the land. They cause deadly floods in low-lying river valleys, but also provide the water southern Asia relies upon for agriculture.

## What is the origin of the word "monsoon"?

The word "monsoon" comes from the Arabic word "mausin," meaning season.

## What are dust devils?

These columns of brown, dust-filled air, which can rise dozens of feet, are not as evil as the name suggests. They are caused by warm air rising on dry, clear days. Winds associated with dust devils can reach up to 60 miles [96.5 kilometers] per hour and cause some damage, but they are not as destructive as tornadoes and usually die out pretty quickly.

## What is the windiest place on Earth?

Mt. Washington, New Hampshire, is the windiest place. In 1934, regular wind speeds were clocked at 231 miles (372 kilometers) per hour.

## Is Chicago really the "windy city?"

Chicago is not the windiest city in the United States. Chicago's average wind speed of 10.4 miles [16.7 kilometers] per hour is beat by Boston (12.5 [20.1]), Honolulu (11.3 [18.2]), Dallas and Kansas City (both 10.7 [17.2]), and especially in the true windy city, Mt. Washington, New Hampshire (35.3 [56.8]).

Chicago, Illinois, is not really the windiest city in the United States (photo by Paul A. Tucci).

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