It's hard to generalize about the climate of a country ranging in
elevation from near sea level to Mount Everest. About the only thing
that can be said is that all but a few parts of Nepal are governed by
the same monsoonal pattern, with temperatures varying according to
elevation.
Five seasons prevail in Nepal, but these are based on more than just
weather: whenever you choose to go, you'll have to weigh other factors,
both positive (mountain visibility, festivals, wildlife) and negative (crowds,
disease).
Probably half of all tourists visit Nepal in the autumn (October to
November), and for good reasons. The weather is clear and dry, and
temperatures aren't too cold in the high country nor too hot in the
Tarai. With the air washed clean by the monsoon rains, the mountains are
at their most visible, making this the most popular time for trekking.
Two major festivals also fall during this season. The downside, however,
is that the tourist quarters are heaving and hustley, prices are higher
and it may be hard to find a decent room, you'll wait ages for food and
for trekking permits, and people are short on ready smiles and chat.
Winter (December and January) weather is for the most part clear and
stable. It isn't especially cold at lower elevations - it never snows in
Kathmandu, and afternoon temperatures are balmy - but the "mists of
Indra" can make mornings dank and chilly (especially in unheated budget
lodgings). Most travellers head down into India, leaving the tourist
areas fairly quiet - too quiet, sometimes, as many restaurants pare down
their menus for the season, and most trekking lodges close. This is an
excellent time to visit the Tarai, where temperatures are relatively
mild.
Spring (February to mid-April) brings warmer temperatures, longer days,
weddings and more festivals. The rhododendrons are in bloom in the hills
towards the end of this period, and in the Tarai the thatch has been cut,
so despite the increasing heat this is the best time for viewing
wildlife. All of which creates another tourist crush, albeit not quite
as bad as in the autumn. The one factor that keeps people away is a
disappointing haze that obscures the mountains from lower elevations,
though it's usually possible to trek above it.
The pre-monsoon (mid-April to early June) is stifling at lower
elevations, and dusty wind squalls are common. People get a little edgy
with the heat; this is the time for popular unrest, but also for the
Kathmandu Valley's great rainmaking festival. Trek high, where the
temperatures are more tolerable.
Nepalis welcome the monsoon (June to September), which breaks the
enervating monotony of the previous months, and makes the fields come
alive with rushing water and green shoots. The rains rinse and renew the
land. This can be a fascinating time to visit, when Nepal is at its most
Nepali, but there are many drawbacks: mountain views are rare, leeches
come out in force along the mid-elevation trekking routes, roads become
impassable, flights get cancelled, and disease runs rampant as the
rising water table brings the entire contents of city sewers to the
surface.
Average temperatures (°C) and rainfall (cm)
|
FEB |
APR |
JUN |
AUG |
OCT |
DEC |
| |
Min Max |
Min Max |
Min Max |
Min Max |
Min Max |
Min Max |
| |
rain |
rain |
rain |
rain |
rain |
rain |
|
Ilam (1200m)
|
10 18
0cm |
16 25
6cm |
18 25
32cm |
9 25
28cm |
16 25
8cm |
8 18
0cm |
|
Janakpur (70m)
|
9 24
1cm |
16 35
4cm |
24 36
23cm |
25 34
24cm |
20 29
5cm |
10 24
0cm |
|
Jumla (2420m)
|
-3 13
4cm |
3 22
3cm |
13 24
7cm |
15 24
17cm |
6 24
4cm |
-5 15
0cm |
|
Kathmandu (1290m)
|
4 20
3cm |
11 27
6cm |
19 29
29cm |
20 28
36cm |
13 26
6cm |
2 20
0cm |
|
Namche (3450m)
|
-6 6
2cm |
1 12
3cm |
6 15
14cm |
8 16
24cm |
2 12
8cm |
-6 7
4cm |
|
Pokhara (80m)
|
8 21
3cm |
15 30
9cm |
20 29
57cm |
21 29
71cm |
17 26
22cm |
7 20
0cm |
|
Sonauli (90m)
|
10 26
1cm |
18 37
6cm |
24 38
28cm |
26 35
41cm |
21 30
8cm |
10 25
0cm |
The monsoon
Listen to these humming downpours in the night
and the doors to godly pleasures will unfold themselves.
- Lekhnath Poudyal (1885-1966), "Thoughts on the Rainy Monsoon"
Nepal's climate is governed by the monsoon , one of the world's great
weather phenomena. A seasonal wind (the word derives from the Arabic for
"season"; the Nepali word for monsoon is barkhaa), the monsoon is driven
by extreme temperature fluctuations in Central Asia. As air over the
Asian landmass warms in late spring and early summer, it rises, sucking
air in from the ocean periphery to take its place. The air drawn from
the south, passing over the Indian Ocean, is laden with moisture; as
soon as it's forced aloft and cooled (whether by updrafts over hot land,
or by a barrier, such as the hills and mountains of Nepal), it reaches
its saturation point and drops its moisture. With the arrival of autumn,
the flow reverses: cooling over the continent blows dry air outwards,
bringing clear, stable conditions.
That's the theory, though in practice this huge, complex system is
affected by countless variables such as land temperatures, jet-stream
patterns, topography and late-season typhoons. The further inland you
are, the harder it is to predict the outcome. Nepal is at the end of the
line of the eastern arm of the South Asian monsoon sweeping up from the
Bay of Bengal, which means it gets a month or so of pre-monsoon - a
period of false storms and dry lightning - before the moist air arrives.
In Nepal, the rains generally advance from east to west in early to
mid-June, and drop more precipitation overall in the east than in the
west. They build slowly, reaching a peak in July and early August, then
taper off again until clear weather returns by early October. Even at
the monsoon's height, however, it doesn't bring continuous torrential
rain - more usually it's intermittent showers and longer overnight
soaks. Local terrain and other factors can affect rainfall considerably:
areas lying in the "rain shadow" north of the Himalaya see very little
monsoon moisture, while south-facing slopes may receive precipitation
long before the plains to the south do. The latter effect is most
dramatic where monsoon winds slam into high ranges with few intervening
foothills, as they do around Pokhara.
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