10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I25 



throughout the year in any one area, seasonal change is primarily a 

 question of rainfall, and the distribution of rain is largely a matter of 

 topography. On the Caribbean slope of Guatemala, which receives 

 the moisture-laden tradewinds from the northeast more or less regu- 

 larly throughout the year, there is no real dry season. On this versant 

 120 to 200 inches of rain are recorded annually, falling on as many 

 as 250 days distributed throughout the 12 months. As would be ex- 

 pected, to the south of the northern mountain ranges there is a region 

 that is very dry, often with desert conditions. Thus, in Chiquimula, 

 in the Department of the same name, the average annual rainfall dur- 

 ing a 7-year period was less than 16 inches, falling on 21 days 

 distributed over only 5 months of the year. In the Motagua River 



Table i. — Relation of temperature to altitude in Guatemala 



Mean annual temperatures Difference 



Number {Fahrenheit) between 



of years , ; '^ ^ maximum 



Altitude included Maxi- Mini- _ and 



Station {feet) in data mum mum Mean minimum 



Puerto San Jose, 



Escuintla 3 3 88.7 75.4 83.8 13.3 



Finca Morelia, 



Chimaltenango 3150 4 87.4 61.3 70.9 26.1 



Guatemala City, 



Guatemala 4900 24 82.0 51.6 64.8 30.4 



Quezaltenango, 



Quezaltenango 7735 11 77.9 35.6 58.5 42.3 



valley there may be as little as 6 inches of rain recorded annually. 

 As one progresses south and west to the region of Los Altos and to 

 the northeastern slopes of the Sierra Madre, the rainfall increases 

 with altitude. On the Pacific slope of the Sierra Madre, which rises 

 out of the coastal plain like a solid wall, there is a pronounced dry and 

 wet season, the latter being caused primarily by the more local south- 

 southwest winds from the Pacific, which blow somewhat irregularly 

 from May through October. Those areas along the slopes of the 

 mountains above 1,500 feet receive large amounts of rainfall, primarily 

 during the 6-month rainy season. The heaviest rainfall occurs during 

 the period between the "Canicula de San Juan" (cessation of rain in 

 the middle of July) and the beginning of the dry season, usually in 

 the month of September. At various stations in the Departments of 

 Retalhuleu and San Marcos more than 190 inches of rain are re- 

 corded. At one station in the Municipality of Malacatan, Department 

 of San Marcos (southwestern Guatemala), almost 390 inches of rain 

 were recorded falling on 160 days over the 12 months of 1945. This 



