The terrain surrounding Pensacola is relatively flat,
and does not stop the passage of transitory storms approaching from the west
and southwest. The two major influences of terrain on weather in the Pensacola area are the Gulf of Mexico and the Mississipi River Valley.
The Gulf of Mexico moderates weather in the local area,
due to land-sea interactions. Tertiary land and sea breezes dominate the
local area as far inland as 40 nm, depending on their intensity. The Gulf
affects local area temperatures during the summer. Once the convective
temperature (generally 10 degrees Fahrenheit (F) above the sea surface
temperature) has been reached, the sea breeze dominates, and creates a
nearly instantaneous 4-7 degree F drop in the air temperature. In
the winter, the Gulf moderates the Polar outbreaks and infrequent Arctic
outbreaks along the coastal region. In the near coastal regions,
relatively warm water temperatures raise the minimum temperatures.
Minimum temperatures below freezing occur more frequently further inland
(more than 10 nm). The Gulf does not stop the northeastward movement of
unstable waves that develop over southern Texas. Generally speaking, thunderstorms
that form over the Gulf and move inland produce heavy precipitation and
occasionally severe weather.
The Mississippi River Valley extends from the Great Plains
to the Gulf and provides a natural way for migratory pressure systems to
enter the coastal regions. In the winter, frequent outbreaks of cP air
(continental polar) and occasional cA air (continental arctic) reach the
coastal area. During the spring and fall, diffused and modified mP
air masses are generally the rule. Frontal systems that affect the local
area must have a deep upper-level trough that is large enough to to force
the Polar Jet deep into the Four Corners region of the southwestern U.S.
or central Texas. Freezing temperatures can be expected locally if this
troughing is followed by a cA air mass.
Forecasters reporting to Pensacola must have knowledge of both mid latitude and tropical meteorology. The local area is subject to subtropical and tropical systems. There are also severe thunderstorms and seasonal fog. However, Pensacola lies well south of the paths of the migratory storm systems that impact the U.S. north of 35 degrees N.
The average summer (June, July, and August) temperature ranges from an average minimum of 74 degrees F. to an average maximum of 88 degree F. with an average of 81 degrees F. Temperatures of 90 degrees F or more occur on the average of 42 days per year. The average winter (December, January, and February) temperature ranges from an average miminum
of 45 degrees F. to an average maximum of 62 degrees F. The daily average
is 53 degrees F. Temperatures at or below freezing occur on average
of 17 days annually. The average dates of the first and last killing frosts
are 9 December and 20 February.
The bluffs located along the northwest section of Pensacola
Bay supply a drainage wind. This drainage wind increases the gradient wind
for 2-4 hours during the early mornings of spring and fall.