ECONOMIC ASPECTS OF CITRUS-FRUIT GROWING IN FLORIDA 9 
_ The average annual wind movement for the west coast is 6.7 miles 
per hour, the average monthly movement being above 5.5 and not 
higher than 7.5 miles per hour. | 
TEMPERATURE 
The temperature for this region is noted for its uniformity. 
Though the summers are long, the extreme of heat is rarely 100° F. 
During the warmest part of the day atmospheric circulation is most 
active, the winds sweeping across the peninsula from ocean or gulf, 
mitigating in a great measure the disagreeable consequences of warm 
days and high humidity. The warmest weather occurs during July 
and August, when maximum temperatures of 100° F. or slightly 
above may be recorded. The mean annual temperature is 72°; 
mean summer temperatures, June to September, range from about 
80 to 82°; and mean winter temperatures, December to February, 
range from 59 to 62°. January is the month of lowest average tem- 
- perature with a mean of 59.9° F. over a period of 20 years, but the 
most severe cold waves have occurred in February. 
Seasons of widespread disaster to fruits and vegetables were Janu- 
ary, 1886; December, 1894; and February, 1895 and 1899, which 
comprehend the extreme conditions that have occurred during the 
fundamental period 1871 to 1912. Authentic data covering a period 
of about 50 years antedating 1871, show that severe cold waves 
occurred in Florida in 1835 and 1857. Other authentic data give 15 
severe freezes in a period of 175 years, or an average of one freeze 
every 11.6 years. During this entire period, however, only three 
freezes, those occurring in 1835, 1886, and in the winter of 1894-95 
are classed as ‘‘great freezes” which killed back young trees and 
severely damaged bearing trees. 
The average date for the first killing frost at Bartow, Polk County, 
is December 19, and the average date of the last killing frost is 
February 11. The date of the earliest killing frost on record is 
November 14, and the date of the latest killing frost on record is 
April 17. Bartow is somewhat lower in elevation as compared with 
most of the district planted to citrus trees. It is possible that, 
because of this lower elevation, Bartow may have experienced low 
extremes in temperatures more often than would be the case on the 
higher citrus land with better air drainage. 
Not many of the growers coming within the scope of this study had 
made any serious preparations to heat their groves in the event oi 
frost. Many groves receive a measure of protection from frosts 
because of location near lakes where the temperature is moderated to 
some extent, and many groves are located on rolling ground which | 
provides good air drainage. But most of the severe freezes which 
have occurred in Polk County have been accompanied by high 
winds so that lakes and windbreaks failed to give absolute protection. 
(Table 6.) | 
102323°—26i_—2 
