FLORIDA GEOLOGICAL SURVEY


a maximum of 56.4 inches at the St. Leo station. In view of the
small deviation of these extreme values from the mean, the
weighted average rainfall of 52.7 inches for the area of
investigation appears to be reasonably accurate.
 The amount of rainfall on the area varies seasonally. About
60 percent of the annual total rainfall occurs during the wet season
from June through September. In the spring and early summer,
local thunderstorms of high intensity and short duration sweep
over the area. Showers occur almost daily, or perhaps several times
a day, during June and July. Heavier and more prolonged rainfalls
occur generally in August and September and are often intensified
by tropical storms that occasionally reach hurricane proportions.
On the other hand, there are periods of a month or more with little
or no rainfall. Periods of below average rainfall usually occur
during the winter season from November to February.
 During wet years the annual rainfall is about twice that of dry
years. The annual and the mean monthly rainfalls for the years
1931-1961 are shown by bar graphs in figure 6. The maximum
annual rainfall during this 31-year period was 70.9 inches in 1959
and the minimum was 34.7 inches in 1961. Both occurred during the
period of the investigation. It is a fortunate circumstance that the
full range of hydrologic conditions was experienced during the
investigation.


 TEMPERATURE

 A knowledge of temperature variations in central Florida is
pertinent to a study of its water resources because of the dominant
influence of temperature on rates of water losses by evaporation
and transpiration.
 The mean monthly temperature in the Green Swamp area ranges
from 610 F. for January to 82' F. for August. The lowest
temperature recorded during the 69-year period of record at the
Clermont station was 180 F. and the highest was 104 F. Daily
temperatures recorded at the U. S. Weather Bureau stations show
that all parts of the area have essentially the same temperature,
ranging no more than 2 to 30 F.
 Killing frosts occur infrequently in this area, and damage to
vegetation, although severe from the standpoint of agriculture,
seldom is great enough to affect the hydrologic factors pertinent
to water supplies.