146 Part II. Chapter 2. 
a rainfall of 20 to 40 inches, while immediately to the eastward in the lee of 
these mountains, it is only from 2 to 6 inches. 
Islands occur also in the areas of least rainfall, and are found at the sources 
of many of the great rivers of the west, such as the Rio Grande which flows 
from a rainfall island found in northern New Mexico and southern Colorado. 
The great swampy areas of the United States are found in regions of highest 
rainfall. This is true for example of the Everglades in Florida, where the 
rainfall is 50—70 inches (127—178 cm) per year. It is also true of the great 
swampy district lying on the coast of North Carolina, where the rainfall is 
60 inches per year, and upward; also the swampy district about the mouth of 
the Mississippi River; but it is not so true of the celebrated swampy. distriet 
lying to the west of the Mississippi along the Gulf coast. About the mouth of 
the Mississippi, the rainfall is above 60 inches (152 cm), while for the celebrated 
swampy district the rainfall is less than 60 inches though it is above 50 inches. 
This wet area has probably been but recently recovered from the Gulf by 
deposits brought down by the great river‘). 
The Great Lakes also influence to some extent the rainfall. In general, 
for instance, it will be found that the rainfall is greater on the east shore of 
Lake Michigan than on the west, the prevailing winds crossing the lake from the 
west. Much the same is true of the east shores of Lake Erie and Lake Ontario. 
Maximum. monthly rainfall. It is of special interest to see in what way 
the rainfall is distributed geographically over the United States with reference 
to the season. A maximum of rainfall in March extends along the Atlantic 
and Gulf coasts from New England to Texas and extends down into the 
p dien ka Florida. It spreads well into the interior and covers the region 
es the eg of the lower lakes, In April, it has passed westward and oc&W 
er > a territory in Arkansas and Louisiana. By May, this maximum 
ie E u Mei. and occupies the central plains, the crest a 
TE ana ee of Davenport, Iowa, around the extreme nofl 
Thes & = asia the vicinity of Cheyenne, Wyoming. He, 
ins are well distributed for greatest usefulness to cropS and growing 
plants. The regions of sum ? ; eis 
mer rainfall ’ interesting. Ther 
an enormous territory in th mely I e 
occurs in Ju The; € United States over which a maximum vainfall 
western Wanlı “ line which represents the crest of this wave 5 = 
ington and ext i Florida 
There is also a ends to the southern part of peninsula ns 
distinct extensi } 1 f the ie 
on of i inity © = 
upper Great Lakes. this area eastward in the vieinity bi 
plains, through Colorado New Mexico and Arizona. 
has ext i 
xtended still farther from the main axis in June, and is found then 
1). HARRINGTO ee En 
of 1891, United Sn ee we: Rainfall and Snow of the United States, compiled to meR Ben 2 
es Department Agriculture, Weather Bureau Bulletin C. Washington nn 
