Pressure Systems. Another feature influencing Kansas weather is a region of semi-permanent high pressure located to the south of the path of the jet stream. The continental land masses tend to break this region into two systems, one located over the Atlantic Ocean and the other over the Pacific. Just as the jet stream does, these features of the circulation pattern also shift further northward in summer, when there is less contrast in temperature between the poles and the equator. The clockwise circulation around high pressure systems creates southerly winds in the western region of the system. These southerly winds pass across the Gulf of Mexico and bring considerable amounts of moisture to the continental interior east of the Rockies during the summer. These warm, moist air masses are often unstable and capable of producing severe thunderstorms. Because of this, a very large portion of the annual precipitation in this region occurs during the summer season. Southeast Kansas, the part of the state nearest the Gulf source of moisture, receives the most rainfall. Western Kansas, deep in the rain shadow of the Rockies and furthest removed from the Gulf, receives an average of about 20 inches less precipitation than does the Southeast.
West-coast and Rocky Mountain chains are extreme examples of how topography influences climate. They lie across the path of the jet stream and have a considerable influence on the atmosphere passing over them. In general, air cools as it rises, and less moisture is required for it to become saturated. Because the air arriving from the Pacific is moist and is pushed upward by the mountains, it soon cools to the point that saturation occurs and clouds are formed. As it rises still higher, moisture as rain or snow may be lost from the moving air stream. As the air passes over the mountain crest, it descends and warms and clouds disappear. The western slopes of mountain chains are relatively moist regions compared to their eastern slopes. Western Kansas lies in the rain shadow of the Rocky Mountains, and almost all of the Pacific moisture has been lost from the air stream by the time it reaches Kansas.
Temperatures in a region depend on the amount of solar energy received and how it is distributed over the globe. These factors, in turn, are influenced by several variables. First, the earth's axis is not vertical to the plane of revolution about the sun. The axis tilts toward the sun during the summer and away from it during the winter. This tilt causes the mid-latitudes to experience marked temperature differences between the seasons. Surprisingly, temperatures are coldest in Kansas when the earth is nearest the sun and warmest when it's furthest away.
Second, land masses heat and cool much more rapidly than large lakes or oceans because less energy is required to change the temperature of soil than of water. For this reason, mid-continent and mid-latitude regions experience much larger ranges of temperatures than coastal regions or the tropics.
Third, elevation above sea level also influences the temperature of a region, as people who have vacationed in the mountains know. Northwest Kansas is over 3,000 feet above sea level compared to some parts of southeast Kansas at less than 1,000 feet elevation. The higher elevation accounts for greater nighttime cooling and lower minimum temperatures on cloudless nights in northwestern Kansas than in other parts of the state.
All of these factors combine in a rather complex way to influence the climate of a region—an influence that extends over very large areas unaffected by state boundaries. So, much of what can be said about the climate of Colby also applies to western Kansas, eastern Colorado, and western Nebraska.