26 PLANT LIFE OF ALABAMA. 
The range between the lowest and highest mean temperatures for a 
period of twenty-three years covers 52°, with 35° in January and 87° 
in July for extremes. The widest range in the extremes of tempera- 
ture observed once in that period covers 104° between the absolute 
minimum of 2° in January' and the absolute maximum of 106° in 
July. 
In the southern division of the State, which is mainly embraced 
within the isothermal lines of 68° and 64° F., the lines of mean annual 
temperature follow with but slight deviation the parallels of latitude. 
Between the isothermal line of 64 and that of 60° extends a central 
belt closely following the terrace that divides the northern and south- 
ern divisions of the State. The lines of mean annual temperature 
of 60° and 62° include its northern division. 
RAINFALL. 
The meteorological region including Alabama receives the supply 
of moisture for its precipitation principally from the Gulf of Mexico. 
In the distribution over time and space the rainfall is of great uni- 
formity. According to the records of the State weather service. 
consisting of observations made at the 48 different stations through 
periods of from two to over thirty years, the annual rainfall for the 
entire State is about 52 inches. Of this amount 14.52 inches falls 
during the winter months, December, January, and February; 14.83 
inches in the spring; 13.21 inches in the summer, and not quite 10 
inches (9.55) in the autumn. The greatest annual rainfall does not 
exceed 65 inches at any place and the least falls not below 41.75 inches. 
The number of rainy days in a year observed during a period of six 
successive years fluctuates between 74 and 117, according to the records 
kept at Montgomery; no periods of wet weather extend over five 
days.° 
Snow falls occasionally in the northern part of the State: usually 
one considerable snow fall occurs during midwinter. In the lower 
part it snows very rarely. 
Such a plentiful and evenly distributed, but not excessive, supply 
of atmospheric moisture, in connection with a mild and equable tem- 
perature, is productive of a highly luxuriant vegetation, which is most 
strikingly exhibited in its arboreal growth. 
WINDS. 
In its correlation with temperature, precipitation, and cloudiness, 
wind exercises a potent influence upon the climate. The prevailing 
"On February 13, 1899 (not included in the above period), the temperature fell at 
Tuscaloosa to 6° or 7° below zero F. and at Mobile to 3° below. 
*P. H. Mell, Climatology of Alabama, op. cit., pp. 28, 29, 59. 
*K. A. Smith, Agricultural Features of Alabama. Report of Geological Survey of 
Alabama for 1880 and 1881. 
