Prophecy: Climate


On the world of Oerth,
local weather is strongly affected by magic, and it is possible
that magic even generates or controls the world’s climate as well.
Certainly, the Flanaess has an unusually long summer and growing
season, especially considering the world’s large axial tilt, which
by rights should produce remarkable seasonal and climatic extremes.
Certain deities and their agents specialize in manipulation of the
atmosphere, including winds, clouds, rain, heat and cold. Such
manipulations are generally meant to keep the weather beneficial to
most worshipers of the gods, though the weather can also be used to
punish transgressors on a large scale.

Spells cast by wizards
and priests can have extraordinary effects on local weather
patterns, too, and new weather-altering spells are developed all
the time. Some kingdoms appear to deliberately alter local
conditions on a day-to-day basis to keep the weather as pleasant as
possible. However, there is concern that great or prolonged weather
changes using magic result in a backlash, altering conditions
elsewhere on the world or even on other planes, particularly the
elemental ones. Some areas of Oerth, particularly over the seas,
are savaged by storms of extreme violence, perhaps unknowingly
driven by magic-use elsewhere.

Beyond this, changes in
climate on Oerth are closely related to latitude. In general, a
change of one degree of latitude will result in a difference of two
degrees Fahrenheit in temperature. Thus, a wizard teleporting from
the equator in the jungles of Hepmonaland to the northernmost
peninsula of the Land of Black Ice, about 60 degrees north
latitude, should experience a sudden drop in temperature of roughly
120 degrees. Local conditions alter this tendency.

The Flanaess, as noted,
has an especially good growing season. Temperatures rarely fall
below freezing in that part of the Flanaess that is below 45
degrees north latitude (roughly the latitude of Perrenland), except
during the two winter months (Sunsebb and Fireseek) and early
spring (Readying), and at night during late spring (Coldeven) and
late autumn (Ready’reat). Even in the depths of winter, rarely more
than a week or two of bitterly cold weather is suffered, with
gradual warming after. Summer lasts five or six months in the
central Flanaess, that area between 4S and 2S degrees north
latitude, approximately the latitudes of the Crystalmists. The
climate here is temperate, with snowfall rare south of latitude 35
degrees (just south of Greyhawk).

The coasts usually
receive more rainfall and remain cooler in the summer and warmer in
the winter than inland areas. Several areas have subtropical
conditions, during which the summers are relatively dry but winters
bring considerable rain. These areas include the Hold of the Sea
Princes, the Pomarj, Ormwal, Idee, the Vast Swamp, Dullstrand, the
northern Lordship of the Isles and the Spindrift Isles.

Tropical conditions
generally exist everywhere south of 20 degrees north latitude.
Affected in particular are the Amedio Jungle, the Tilvanot
Peninsula, the southern Lordship of the Isles and all of
Hepmonaland. Here, it is hot and rainfall is abundant year-round.
Hurricanes are known to occur, generally moving from southwest to
northeast except around Hepmonaland, where they usually come
directly from the west or southwest, moving against the general
flow of air.

The arid Sea of Dust is
a blast furnace during the summer, but it remains hot in the
daytime all year long and rainfall is rare. This area’s horrific
weather appears to be maintained by the ancient Stone Circles of
Tovag Baragu, in a manner that is not well understood.

High elevations in the
Yatils/ Barrier Peaks/ Crystalmists/ Hellfurnaces chain and in the
Thillonrian PeninsuWs Corusks/ Griffi/ Rakers chain remain
snowbound all year long, with glaciers and alpine conditions above
the tree line. Parts of the Hellfurnaces remain above freezing all
year long, from active volcanism and the influence of what may be
numerous gates to the Elemental Plane of Fire. The Lortmils and
Glorioles have only a few snow-capped peaks.

Most regions between 45
and 55 degrees north latitude (the latitudes of the Barrens and the
lands of Itiz) count as subarctic, with cool, dry summers during
which the ground thaws for only a few months. This region is very
close to the Northern Border of Day and Night (as Oerth’s arctic
circle is called), north of which the length of day and night alter
greatly. The Thillonrian Peninsula receives more rain and snowfall
than interior areas such as the Barrens, Iuzs homeland and the land
of the Wolf Nomads, which are cold steppeland with permafrost
tundra farther north. Barbarians of the Thillonrian Peninsula
practice limited agriculture.

An exception to the
above are those regions adjacent to the Dramidj Ocean, which is
known for its unusually warm currents. Zeif, Tusinit, Ekbir and the
western half of the lands controlled by the Tiger Nomads are all
temperate, with respectable rainfall and the same growing seasons
as the central Flanaess. Fog is common in the winter here, as cold
air from the north passes over the warm sea. Icebergs are often
shrouded in fog.

Prevailing winds in the
Flanaess tend to be from the north and northeast in autumn and
winter, and from the east and southeast in spring and summer. The
wintry north wind is often called “Telchur’s breath,” after the
Oeridian god of the north, and the spring wind from the east is
called “Atroa’s laugh,” for the Oeridian goddess of the east and
springtime. Mountain ranges and the like may alter this.

When they flow against
high hills and mountains, moisture-laden winds from the east cool,
causing rainfall. As the winds cross the hills and mountains, they
warm up, retaining their moisture. Thus, the western side of many
mountain ranges are dryer than the eastern side. This becomes
especially apparent when looking at the west and east sides of the
Barrier Peaks/ Crystalrnists/Hellfurnaces chain, though the western
side is also more arid because of magical influences. Elsewhere,
the Kingdom of Surindi is wetter than the Ahlissan Principality of
Naeric to the west, thanks to the Hollow Highlands, but is drier
than DuIlstrand and old Medegia, thanks to the Hestmarks. The
natural depression found at the joining of these two hilly chains
just south of Sunndi forms the Vast Swamp. The eastern Abbor-Alz
help keep the Bright Desert dry, yet also feed the Gnatmarsh with
abundant rain.