140 



Our Surroundings 



water but retains the heat for a shorter time. Hence, with the 

 coming of summer, the land area of the United States, being in 

 a northern continent, becomes much more heated than the waters 

 bordering it. On this account, low pressure develops over the 

 country and, as a result, winds blow more or less inland. This 

 causes prevailing southerly winds which bring hot waves. 



On the other hand, with the coming of winter, the large bodies 

 of water that wash the shores of the country retain their heat 

 much longer than the land areas. High pressure develops over 

 the land areas and causes winds to blow seaward. As a result, 

 west and northwest winds blow over the greater part of the United 

 States east of the Rocky Mountains and bring cold waves. 



Most of the cyclonic storms 

 that occur in the United States 

 start over the waters of the 

 Pacific, northwest of the coun- 

 try. The weather maps show 

 that they come into the United 

 States near the northwestern 

 boundary. They usually blow 

 over the land in a southeasterly 

 direction until they pass the 

 middle section. Then they turn 

 to the northeast, leaving the 

 country by the St. Lawrence 

 valley. Sometimes the storms, as they come from the Rocky 

 Mountain system, veer to the south and even reach the coast of 

 the gulf of Mexico. These also commonly leave the country 

 in a northeasterly direction, passing out over the Atlantic Ocean. 

 Weather maps indicate that some cyclones start in waters off the 

 southwest coast of the country and pass over it through Arizona 

 and New Mexico, then taking the same direction as the other 

 storms. The movements of all cyclonic storms seem to follow 

 in a general way the course of the prevailing westerlies of the 

 middle latitudes. 



Weather Lore. Although weather science, commonly called 

 meteorology, is a new science not yet a century old, men for 



U. S. Weather Bureau. 



PATHS OF STORMS ACROSS 

 THE UNITED STATES 



Notice how these storms tend toward the 

 St. Lawrence valley. 



