complex. Depending upon the depth to which they study the area,
climatologists list six or more climatic subzones. The country lies on
the line of transition between the strongly contrasting Eastern European
continental and the Mediterranean climatic zones, and its mountains and
valleys are local factors that act as barriers or channels to the air
masses, contributing to sharp contrasts in weather over relatively short
distances. The Black Sea, although too small to be a primary influence
over much of the country's weather, also affects the immediate area
along its coastline.

In general, continental systems prevail in the north. They are
characterized by hot summers, cold winters, and precipitation well
distributed throughout the year, a major portion of it in early summer
thunderstorms. The Mediterranean climate that is influential most of the
time in the south has mild, damp winters but hot, dry, rain-free
summers. The Stara Planina marks the lower limits of the area in which
continental air masses circulate freely in typical circumstances. In the
area between them and the Danube River there is an extension of the
climate that is common to east-central Europe and adjoining regions of
the Soviet Union.

In the same fashion, the Rodopi marks the northern limits of domination
by Mediterranean weather systems. The southern slopes of these mountains
are sufficiently mild to merit the region's being called the Green
Greece or Bulgarian California.

The area in between, which includes the Thracian Plain, is influenced by
both types of climate, but more of the time by continental systems. The
result is a plains climate resembling that of the corn belt in the
United States, which is characterized by long summers and high humidity.
The climate is generally more severe than that of Spain and the portions
of Italy, France, and Soviet Georgia that are in the same latitude.
Because it is a transitional area and the Mediterranean systems may
prevail for most of some seasons or retreat from the scene altogether in
other seasons, average temperatures and precipitation are erratic and
may vary widely from year to year.

Precipitation over the country averages about twenty-five inches a year
and, when it is distributed normally throughout the seasons, it is
satisfactory for most agricultural crops. Dobrudzha, in the northeast,
the Black Sea coastal area, and parts of the Thracian Plain usually
receive less than twenty inches. The r