West Bengal has a tropical climate. The plains are hot
except during the short winterseason.
The mountanious region in the north is cold. On account of its altitude
but there humidity is high. The classical tradition speaks of six seasons-Spring,
Summer, the rainy, Autumn, mild Winter and severe Winter. Only
four clearly marked seasons with a brief interregnum of spring are observed,
namely the hot season, the rainy season, the post monsoon season corresponding
to autumn and the cold season. The hot season lasts from mid-March to
mid-June, with the day temperature ranging from 38o C to 45oC
in different parts of the state. At nights, a cool southerly breeze carrying
moisture from the Bay of Bengal is usually present. The high temperature
often causes troughs of low pressure to form on the plains which are compensated
by sudden briefs storms known as kal-baisakhi or 'nor-westers', accompanied
by thunder showers. These summer storms can be quite destructive. The
hills of Darjeeling district are pleasantly cool in summer, the higher
reaches are sometimes enveloped in heavy fog. On some days, one is rewarded
by the sight of the majestic snow-girt Kanchanjunga and the eastern Sikkim
ranges and the greenness of the wooded hills and gorges that abound on
The monsoon arrives by a middle of June. Its scouts start
arriving about two weeks before its normal onset. This is called the Chhota
monsoon which breaks the hot spell of summer. The monsoon
rains in west Bengal are caused solely by the current of wind from the
Bay of Bengal.
Variability is a characteristic feature of the
monsoon in west Bengal as well as Bangladesh and Orissa which all receive
the impact of the south-west Bay current. Breaks in the continuity of
rain are not unusual, the resultant thoughts of low pressure develop into
cyclone storms especially towards the end of the season and in early autumn.
A welcome change in the weather begins to be distinctly
felt towards the end of September. Autumn in West Bengal is the season
for festivity in the fields the golden grain of paddy starts ripening
and is harvested towards the end of the season. The conclusion of the
round of the festivities marks the onset of the winter in mid-November.
Winter, which lasts about three months, is mild over
the plains, the average minimum temperature not falling 15o
C. It is attended by a cold and dry northern wind, substantially lowering
the humidity level. Winter is the season for the rabi crops-pulses, potato
and vegetables and citrus fruits that grow on the Darjeeling hills. There
occurs a short interregnum of clouds and rain usually the last week of
December and the first week of January, caused by the incursion of the
western monsoon coming all the way from the Arabian Sea. The cold is severe
on the hills and there are sometimes sleet and snow on the higher reaches
during the days of rain.
The weather gets warmer by the middle February, which
heralds a brief spring season lasting about a month during which
the deciduous trees break out in young green leaves and flowers. But this
mellow season is too short-lived and the heat is turned on until
with the coming of April, clammy summer comes in full blast and the annual
cycle of seasons rolls on once again.