THE TERM climate refers to the long-term averages of insolation (solar radiation absorbed by Earth), temperature, precipitation, cloud cover, air masses, atmospheric pressure, winds, and cloud coverage. Of these, temperature and precipitation are the most important factors in establishing climate type. A place may have rain on one day, clear conditions for a week, and then have cloudy skies the next day followed by a hailstorm. The conditions described here would certainly be familiar to a resident of the Midwest in the United States. Daily weather variability in any given place may be quite dramatic. Or the weather may be predictably uniform from day to day. The equatorial regions exhibit this kind of weather: warm temperatures, afternoon showers, slightly cooler nights, and then the repeat of the preceding day’s weather. Whether the daily weather occurrences at a place are extremely variable or predictably uniform, it is the long-term averages of the weather factors that will be used to determine the climate of a place. Scientists in early Greece devised a very simple and straightforward climatic system for the Earth, as they knew it. The system was composed of three zones or klimata. The zone occupied by the Greeks and other culture groups living near the Mediterranean Sea was called the Temperate Zone. This zone had temperature and precipitation values that made it ideal for human occupation. To the south of the temperate zone was the Torrid Zone, an area simply too hot and debilitating for humans to survive. At the time of the development of this climatic system, no one from the temperate zone had traveled very far to the south and certainly not to the equatorial area. Consequently, a great deal of speculation centered on the region and what manner of protection any inhabitants would have to ward off the blistering rays of the sun. There was conjecture that a resident in this region would have feet large enough to extend over his head umbrella fashion to block the sun’s rays. To the north of the Temperate Zone was the Frigid Zone, the unexplored area too cold for humans to survive. As simplistic as this three-zone system may sound today, it was nevertheless based on sound logic: Places to the south of the Greek homeland are warmer and places to the north are colder. These are true observations. However, today we can add immeasurably to the descriptions of our climatic systems and refine them to take into account even subtle changes from place to place.