ecological characterization atlas of coastal alabama - Data Center

CLIMATOLOGY
AND HYDROLOGY
INTRODUCTION
This section relates
coastal Alabama . Included
affects the area, stream
availability and quality .
coastal estuaries are also
CLIMATE
Temperature
information on water availability and its use in
is a description of the coastal climate and how it
and river discharge, and surface and ground water
Currents and their effects on salinities in the
discussed .
The climate of coastal Alabama is primarily humid subtropical , due to the
warmi ng i nfl uence of the Gul f of Mexico . Thi s l arge warm-water surface i s a
major contributor to warm, humid summers, and mild winters, with a fairly
consistent range of temperature extremes (Lineback 1973) .
Coastal Alabama air temperatures are relatively mild, with an average
annual tem perature in Mobile of 20 °C (68 °F) . Mean annual temperature
variation is approximately 10 °C (18 °F) (Table 31) . Summer temperatures are
rarely high ranging between 21 and 32 °C (70 and 90 °F) . Temperatures in
winter generally range between 4 to 16 °C (40 and 60 °F), with temperatures
below freezing occurring on an average of 22 days per year . Periods of
freezing temperatures generally do not last more than 2 or 3 days . The
lowest mean monthly temperatures, 10 °C (50 °F), occur in January, while July
produces the highest average temperatures (28 °C, 82 °F) . Temperature
extremes in the Mobile area vary from a maximum of 40 °C (104 °F) (July 1952)
to a low of -18 °C (-1 °F) (February 1899) (National Climate Center 1980) .
Mobile and Baldwin Counties have a growing season ranging from 230 days
in the northern sector to 300 days in areas near the coast . The first
killing frost occurs in early November in the northern parts of the counties
and early December in areas near the coast . The last killing frost occurs in
mid-February near the coast (O'Neil and Mettee 1982) .
Precipitation
The normal annual rainfall in coastal Alabama is the highest in the state
and among the highest in the United States . Average annual rainfa ll in the
Mobile area is about 162 .5 cm (64 inches) (Table 32) . Rainfall is fairly
evenly distributed throughout the year with a slight maximum at the height of
the summer thunderstorm season in July and a slight minimum during the late
fall in October .
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