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The characteristic features of the climate of Malaysia are uniform
temperature, high humidity and copious rainfall and they arise
mainly
from the maritime exposure of the country.
Winds are generally
light. Situated at the equatorial doldrum area, it is extremely rare
to have a full day with completely clear sky even in periods of
severe drought. On the other hand, it is also rare to have a stretch
of a few days with completely
no sunshine except during the northeast monsoon seasons.
 Wind flow in Malaysia
Though the wind over the country is generally light and variable,
there are, however, some uniform periodic changes in the wind flow
patterns. Based on these changes, four seasons can be distinguished,
namely, the southwest monsoon, northeast monsoon and two shorter
inter monsoon seasons.
The southwest monsoon is usually established in the later half of
May or early June and ends in September. The prevailing wind flow is
generally south westerly and light, below 15 knots.
The northeast monsoon usually commences in early November and ends
in March. During this season, steady easterly or north-easterly
winds of 10 to 20 knots prevail. The more severely affected areas
are the east coast states of Peninsular Malaysia where the wind may
reach 30 knots or more during periods
of intense surges of cold air from the north (cold surges).
The winds during the two inter monsoon seasons are generally light
and variable. During these seasons, the equatorial trough lies over
Malaysia.
It is worth mentioning that during the months of April to November,
when typhoons frequently develop over the west Pacific and move
westwards across the Philippines, south-westerly winds over the
northwest coast of Sabah and Sarawak region may strengthen reaching
20 knots or more.
As Malaysia is mainly a maritime country, the effect of land and sea
breezes on the general wind flow pattern is very marked especially
over days with clear skies. On bright sunny afternoons, sea breezes
of 10 to 15 knots very often develop and reach up to several tens of
kilometre inland. On clear nights, the reverse process takes place
and land breezes of weaker strength can also develop over the
coastal areas.
 Rainfall Distribution
The seasonal wind flow patterns coupled with the local topographic
features determine the rainfall distribution patterns over the
country. During the northeast monsoon season, the exposed areas like
the east coast of Peninsular Malaysia, Western Sarawak and the
northeast coast of Sabah experiences heavy rain spells. On the other
hand, inland areas or areas which are sheltered by mountain ranges
are relatively free from its influence. It is best to describe the
rainfall distribution of the country according to seasons.
Seasonal Rainfall Variation in Peninsular Malaysia
The seasonal variation of rainfall in Peninsular Malaysia is of
three main types:
(a) Over the east coast districts, November, December and January
are the months with maximum rainfall, while June and July are the
driest months in most districts.
(b) Over the rest of the Peninsula with the exception of the
southwest coastal area, the monthly rainfall pattern shows two
periods of maximum rainfall separated by two periods of minimum
rainfall. The primary maximum generally occurs in October - November
while the secondary maximum generally occurs in April - May. Over
the north-western region, the primary minimum occurs in January -
February with the secondary minimum in June - July while elsewhere
the primary minimum occurs in June - July with the secondary minimum
in February.
(c) The rainfall pattern over the southwest coastal area is much
affected by early morning "Sumatras" from May to August with the
result that the double maxima and minima pattern is no longer
discernible. October and November are the months with maximum
rainfall and February the month with minimum rainfall. The March -
April - May maximum and the June -July minimum are absent or
indistinct.
Seasonal Rainfall Variation in Sabah and Sarawak
The seasonal variation of rainfall in Sabah and Sarawak can be
divided into
five main types:
(a) The coastal areas of Sarawak and northeast Sabah experience a
rainfall regime of one maximum and one minimum. While the maximum
occurs during January in both areas, the occurrence of the minimum
differs. In the coastal areas of Sarawak, the minimum occurs in June
or July while in the northeast coastal areas of Sabah, it occurs in
April. Under this regime, much of the rainfall is received during
the northeast monsoon months of December to March. In fact, it
accounts for more than half of the annual rainfall received on the
western part of Sarawak.
(b) Inland areas of Sarawak generally experience quite evenly
distributed annual rainfall. Nevertheless, slightly less rainfall is
received during the period June to August which corresponds to the
occurrence of prevailing south-westerly winds. It must be pointed out
that the highest annual rainfall area in Malaysia may well be found
in the hill slopes of inland Sarawak areas. Long Akah, by virtue of
its location, receives a mean annual rainfall of more than 5000 mm.
(c) The northwest coast of Sabah experiences a rainfall regime of
which two maxima and two minima can be distinctly identified. The
primary maximum occurs in October and the secondary one in June. The
primary minimum occurs in February and the secondary one in August.
While the difference in the rainfall amounts received during the two
months corresponding to the two maxima is small, the amount received
during the month of the primary minimum is substantially less than
that received during the month of the secondary minimum. In some
areas, the difference is as much as four times.
(d) In the central parts of Sabah where the land is hilly and
sheltered by mountain ranges, the rainfall received is relatively
lower than other regions and is evenly distributed. However, two
maxima and two minima can be noticed, though somewhat less distinct.
In general, the two minima occur in February and August while the
two maxima occur in May and October.
(e) Southern Sabah has evenly distributed rainfall. The annual
rainfall total received is comparable to the central part of Sabah.
The period February to April is, however slightly drier than the
rest of the year.
 Temperature Distribution
Being an equatorial country, Malaysia has uniform temperature
throughout the year. The annual variation is less than 2°C except
for the east coast areas of Peninsular Malaysia which are often
affected by cold surges originating
from Siberia during the northeast monsoon.
Even there, the annual variation is below 3°C.
The daily range of temperature is large, being from 5°C to 10°C at
the coastal stations and from 8°C to 12°C at the inland stations but
the excessive day temperatures which are found in continental
tropical areas are never experienced. It may be noted that air
temperature of 38°C has very rarely been recorded in Malaysia.
Although the days are frequently hot, the nights are reasonably cool
everywhere.
Although the seasonal and spatial temperature variations are
relatively small, they are nevertheless fairly definite in some
respects and are worthy of mention. Over the whole Peninsula, there
is a definite variation of temperature with the monsoons and this is
accentuated in the east coast districts. April and May are the
months with the highest average monthly temperature in most places
and December and January are the months with the lowest average
monthly temperature. The average daily temperature in most districts
to the east of the Main Range is lower than that of the
corresponding districts west of the Main Range. The differences in
the average values in the east and the west are due almost entirely
to the low day temperatures experienced in the eastern districts
during the northeast monsoon as a result of rain and greater cloud
cover. At Kuala Terengganu, for example, the day temperature rarely
reaches 32°C during the northeast monsoon and often fails to reach
27°C. A number of occasions have been recorded on which the
temperature did not rise above 24°C which is quite frequently the
lowest temperature reached during the night in most districts. Night
temperatures do not vary to the same extent, the average usually
being between21°C to 24°C. Individual values can fall much below
this at nearly all stations, the coolest nights commonly follow some
of the hottest days.
 Relative Humidity
As mentioned earlier, Malaysia has high humidity. The mean monthly
relative humidity falls within 70to 90%, varying from place to place
and from month to month. For any specific area, the range of the
mean monthly relative humidity varies from a minimum of 3% to a
maximum of about 15%. In Peninsular Malaysia, the minimum range of
mean relative humidity varies from a low 84% in February to a high
of only 88% in November. The maximum range is found in the northwest
area of the Peninsula (Alor Setar) where the mean relative humidity
varies from a low of 72% in February to a high of 87%. It is
observed that in Peninsular Malaysia, the minimum relative humidity
is normally found in the months of January and February except for
the east coast states of Kelantan and Terengganu which have the
minimum in March. The maximum is however generally found in the
month of November.
As in the case of temperature, the diurnal variation of relative
humidity is much greater as compared to the annual variation. The
mean daily minimum can be as low as 42% during the dry months and
reaches as high as 70% during the wet months. The mean daily
maximum, however, does not vary much from place to place and is at
no place falls below 94%. It may reach as high as nearly 100%.
Again, the northwest states of Kedah and Perlis have the largest
diurnal variation of relative humidity.
 Sunshine and Solar Radiation
Being a maritime country close to the equator, Malaysia naturally
has abundant sunshine and thus solar radiation. However, it is
extremely rare to have a full day with completely clear sky even in
periods of severe drought. The cloud cover cuts off a substantial
amount of sunshine and thus solar radiation. On the average,
Malaysia receives about 6 hours of sunshine per day. There are,
however, seasonal and spatial variations in the amount of sunshine
received. Alor Setar and Kota Bharu receive about 7 hours per day of
sunshine while Kuching receives only 5 hours on the average. On the
extreme, Kuching receives only an average of 3.7 hours per day in
the month of January. On the other end of the scale, Alor Setar
receives a maximum of 8.7 hours per day on the average in the same
month.
Solar radiation is closely related to the sunshine duration. Its
seasonal and spatial variations are thus very much the same as in
the case of sunshine.
Source - Malaysia Meteorological Service
information - details -
regarding
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