Myanmar undergoes an annual three season cycle that
follows the classic dry and wet monsoon climate pattern
common to other parts of mainland South-East Asia. The
south-west monsoon starts between mid-May and mid-June,
bringing frequent rains that continue into late October. The
rain tends to fall mainly in the afternoons and evenings.
Although it takes the edge off the intense heat, it does
tend to make things unpleasantly humid. Generally speaking,
travelling in the rainy season is not particularly
difficult, though unpaved roads may occasionally be
impassable. In Central Myanmar it rains most during August
and September, when occasional floods may occur.
The November to May dry period that follows begins with
lower relative temperatures because of the influences of
Asia's north-east monsoon. This second monsoon bypasses all
but the south-easternmost reaches of Myanmar below Myeik (Mergui)
but results in cool breezes throughout the country. As a
result, during December and January the temperature can drop
to near freezing at night in the highlands of the
Kalaw-Taunggyi area.
In February the temperatures start to rise, and during
March, April and May it can be unpleasantly hot. In Yangon
the temperature often tops 40*C and in Mandalay and Bagan
part of the 'dry zone' lying in the rain shadow of the
Rakhaing Yoma (Arakan Range) -- it gets even hotter. The
annual water festival, when people douse each other with
cold water, takes places in April at the height of the hot
season.
Dry season rains known as mango showers occasionally bring
welcome but temporary relief. In May the rains start as the
south-west monsoon again sweeps northward from the Indian
Ocean. In October the rain tapers off and you're back to the
cool, dry winter season.
The geography of Myanmar considerably affects the monsoon
rains. The delta region around Yangon gets about 250cm a
year, but the rainfall rapidly diminishes as the monsoon
continues north; the central area of Myanmar (which includes
Bagan) is a large, comparatively dry zone with 60 to 110cm
of rain a year. Then, north of Mandalay, the hill ranges
force the winds higher and the rain again gets heavier,
reaching a drenching annual total of around 350cm. The
Rakhaing coastal area near Bangladesh and the Tanintharyi
coastal strip beside southern Thainland are exposed to the
full force of the south-west monsoon rains, which are often
held over the region by the mountain ranges inland. Thus
these coastal areas get very heavy rainfall; Sittwe receives
over 500cm a year, Mawlamyaing around 440cm, most of which
falls during the south-west monsoon.
