Paraguay experiences a subtropical climate in the Paraneña
region and a tropical climate in the Chaco. The Paraneña region is
humid, with abundant precipitation throughout the year and only
moderate seasonal changes in temperature. During the Southern
Hemisphere's summer, which corresponds to the northern winter, the
dominant influence on the climate is the warm sirocco winds blowing
out of the northeast. During the winter, the dominant wind is the
cold pampero from the South Atlantic, which blows across Argentina
and is deflected northeastward by the Andes in the southern part of
that country. Because of the lack of topographic barriers within
Paraguay, these opposite prevailing winds bring about abrupt and
irregular changes in the usually moderate weather. Winds are
generally brisk. Velocities of 160 kilometers per hour have been
reported in southern locations, and the town of Encarnación was
once leveled by a tornado.
The Paraneña region has only two distinct seasons: summer from
October to March and winter from May to August. April and September
are transitional months in which temperatures are below the
midsummer averages and minimums may dip below freezing.
Climatically, autumn and spring do not really exist. During the
mild winters, July is the coldest month, with a mean temperature of
about 18°C in Asunción and 17°C on the Paraná Plateau.
There is no
significant north-south variation. The number of days with
temperatures falling below freezing ranges from as few as three to
as many as sixteen yearly, and with even wider variations deep in
the interior. Some winters are very mild, with winds blowing
constantly from the north, and little frost. During a cold winter,
however, tongues of Antarctic air bring subfreezing temperatures to
all areas. No part of the Paraneña region is entirely free from the
possibility of frost and consequent damage to crops, and snow
flurries have been reported in various locations.
Moist tropical air keeps the weather warm in the Paraneña region
from October through March. In Asunción the seasonal average is
about 24°C, with January--the warmest month--averaging
Villarrica has a seasonal mean temperature of 21°C and a
mean of 27°C. During the summer, daytime temperatures reaching
are fairly common. Frequent waves of cool air from the south,
however, cause weather that alternates between clear, humid
conditions and storms. Skies will be almost cloudless for a week to
ten days as temperature and humidity rise continually. As the soggy
heat nears intolerable limits, thunderstorms preceding a cold front
will blow in from the south, and temperatures will drop as much as
15°C in a few minutes.
Rainfall in the Paraneña region is fairly evenly distributed.
Although local meteorological conditions play a contributing role,
rain usually falls when tropical air masses are dominant. The least
rain falls in August, when averages in various parts of the region
range from two to ten centimeters. The two periods of maximum
precipitation are March through May and October to November.
For the region as a whole, the difference between the driest and
the wettest months ranges from ten to eighteen centimeters. The
annual average rainfall is 127 centimeters, although the average on
the Paraná Plateau is 25 to 38 centimeters greater. All subregions
may experience considerable variations from year to year. Asunción
has recorded as much as 208 centimeters and as little as 56
centimeters of annual rainfall; Puerto Bertoni on the Paraná
Plateau has recorded as much as 330 centimeters and as little as 79
In contrast to the Paraneña region, the Chaco has a tropical
wet-and-dry climate bordering on semi-arid. The Chaco experiences
seasons that alternately flood and parch the land, yet seasonal
variations in temperature are modest. Chaco temperatures are
usually high, the averages dropping only slightly in winter. Even
at night the air is stifling despite the usually present breezes.
Rainfall is light, varying from 50 to 100 centimeters per year,
except in the higher land to the northwest where it is somewhat
greater. Rainfall is concentrated in the summer months, and
extensive areas that are deserts in winter become summer swamps.
Rainwater evaporates very rapidly.
Data as of December 1988