In Nepal there are different climates according to altitude: the sub-tropical climate with a rainy season in the southern flat strip, the temperate climate of low mountains, and the cold mountain climate of the Himalayas.
Rainfall is abundant in the period of the summer monsoon (June to early October), which, however, penetrates with difficulty in some sheltered inland valleys and on the northern slopes. On the southern slopes, at equal altitude the east is rainier than the west.

In the thin southern plain, a region known as Terai, the climate is that of the Indo-Gangetic plain, which is also found in northern India. In winter, it's sunny and mild, with an average temperature around 15 °C (59 °F) in January, pleasantly warm during the day but cool at night, sometimes even cold. In March, the temperature rises considerably and it begins to be hot, while from April to June there's a scorching heat, and highs can reach or exceed 40 °C (104 °F).
Here are the average temperatures of Nepalganj (or Nepalgunj).
Average temperatures - Nepalganj

Nepalganj	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Nepalganj	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	9	12	16	21	25	26	26	26	25	21	15	10
Max (°C)	21	25	31	36	37	36	33	33	32	31	28	23
Min (°F)	48	54	61	70	77	79	79	79	77	70	59	50
Max (°F)	70	77	88	97	99	97	91	91	90	88	82	73

In June, the summer monsoon arrives, characterized by heavy rains, in the form of downpours and thunderstorms. The monsoon arrives first in the east, on early June, while in the west it comes in the middle of the month or so. The temperature decreases, the maximum dropping to around 32 °C (90 °F) in July and August, but the humidity increases, making the heat muggy. The rains are intense especially in July and August, when they exceed 300 millimetres (12 inches) per month, but in certain areas at the foot of the mountains, especially in the east of the country, they can exceed 600 mm (23.5 in) per month.
Here is the average precipitation in Nepalganj.
Average precipitation - Nepalganj

Nepalganj	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Nepalganj	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	20	25	9	8	30	155	310	325	215	40	7	8	1152
Prec.(in)	0.8	1	0.4	0.3	1.2	6.1	12.2	12.8	8.5	1.6	0.3	0.3	45.4
Days	1	1	1	1	4	10	17	17	10	4	1	1	68

The monsoon starts to withdraw from early October in the west, and about a week later in the east. The weather returns to be sunny, and even though October is still a hot month, the humidity decreases and the temperature at night becomes a bit cooler.
In the easternmost part of the flat area (see Biratnagar), the heating in the period from March to June is limited, so that the average maximum temperature reaches 33/34 °C (91/93 °F) in April and May. Here, already in the second half of April, the first afternoon thunderstorms occur, prior to the arrival of the monsoon itself.
Above 800/1,000 metres (2,600/3,300 feet), the climate becomes temperate, while the rainfall pattern remains the same. In Pokhara, at 800 metres (2,600 feet), the average goes from 13.5 °C (56 °F) in January to 26 °C (79 °F) in July and August.
Average temperatures - Pokhara

Pokhara	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Pokhara	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	7	9	13	16	18	21	22	22	21	17	12	8
Max (°C)	20	22	27	30	30	31	30	30	29	28	24	21
Min (°F)	45	48	55	61	64	70	72	72	70	63	54	46
Max (°F)	68	72	81	86	86	88	86	86	84	82	75	70

Here the rains are plentiful, because the city is located at the foot of the Annapurna Range, therefore the summer monsoon is particularly intense, because the southern currents are forced to rise when they encounter the mountain slopes: rainfall amounts to 3,900 mm (153 in) per year, including even 940 mm (37 in) in July, and 865 mm (34 in) in August. This is the rainiest city of Nepal. In winter there is little rain here as well, but there can be some atmospheric instability already in spring, with significant thunderstorms in April and May. Here is the average precipitation.
Average precipitation - Pokhara

Pokhara	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Pokhara	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	25	35	60	130	360	670	940	865	640	140	20	20	3900
Prec.(in)	1	1.4	2.4	5.1	14.2	26.4	37	34.1	25.2	5.5	0.8	0.8	153.5
Days

In the capital Kathmandu, at 1,400 metres (4,600 feet) above sea level, the climate is mild. The average January temperature is around 11 °C (51.5 °F), but the temperature range is high, so it gets cold at night, while during the day the sun makes the air mild. Summer is hot, with highs around 27/29 °C (81/84 °F) for a long period, from April to September. Here are the average temperatures.
Average temperatures - Kathmandu

Kathmandu	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Kathmandu	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	2	4	8	12	16	19	20	20	18	13	8	4
Max (°C)	19	21	25	28	29	29	28	29	28	27	24	20
Min (°F)	36	39	46	54	61	66	68	68	64	55	46	39
Max (°F)	66	70	77	82	84	84	82	84	82	81	75	68

Annual rainfall amounts to 1,400 mm (55 in), of which 115 mm (4.5 in) already in May (due to thunderstorms preceding the monsoon), even 360 mm (14.2 in) in July, which is the rainiest month, still 185 mm (7.3 in) in September, and 60 mm (2.4) in October, concentrated in the first part of the month, before the monsoon withdraws. During the monsoon period, the sky is often cloudy, so it's difficult to spot the highest mountains of the Himalayas. Here is the average precipitation.
Average precipitation - Kathmandu

Kathmandu	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Kathmandu	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	15	15	30	55	115	255	360	315	185	60	10	15	1425
Prec.(in)	0.6	0.6	1.2	2.2	4.5	10	14.2	12.4	7.3	2.4	0.4	0.6	56.1
Days	2	3	4	6	12	17	23	22	15	4	1	1	110

In Kathmandu, and in Nepal in general, the sun shines quite often in winter, and very often in spring, before the monsoon, while in the rainy season, especially from July to September, the sky is often cloudy.
Sunshine - Kathmandu

Kathmandu	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Kathmandu	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	6	6	8	10	7	6	3	3	4	6	6	6

Going up in altitude, temperature and rainfall vary not only with altitude, but also with slope exposure, however, since most of the mountains of Nepal are situated in the southern side, the temperature is relatively mild even at high altitudes.
Here are the average temperatures of Jumla, located at 2,300 metres (7,500 ft).
Average temperatures - Jumla

Jumla	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Jumla	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	-5	-3	0	4	8	13	16	15	12	4	-2	-4
Max (°C)	14	15	18	22	24	26	25	25	24	22	19	16
Min (°F)	23	27	32	39	46	55	61	59	54	39	28	25
Max (°F)	57	59	64	72	75	79	77	77	75	72	66	61

Usually the average temperature in January drops below freezing (0 °C or 32 °F) above 3,000 metres (9,800 ft). Above 3,600 metres (11,800 ft), the subarctic climate zone begins, that is, where the average temperature of the warmest month does not exceed 10 °C (50 °F).
In inland areas, the summer monsoon penetrates with more difficulty, so much so that precipitation doesn't go above 100/150 mm (4/6 in) per month in the rainiest months, which are even here July and August. Some particularly sheltered inland valleys receive still less rainfall, and have a desert or semi-desert landscape, such as the kingdom of Mustang, which is located in an arid valley north of the massifs of Annapurna and Dhaulagiri.
In Nepal, some of the highest mountains on Earth are found: Mount Everest, the highest, with its 8,848 metres (29,029 feet), on the border with China; Kanchenjunga, the third highest mountain in the world, 8,586 metres (28,169 feet), on the border with the Indian state of Sikkim; Lhotse, the fourth, 8,516 metres (27,940 feet), located just 3 kilometres (2 miles) south-east of Everest and still on the border with China; Makalu, the fifth, 8,481 metres (27,766 feet), 20 km (12 mi) south-east of Evererst and still on the border with China; Cho Oyu, the sixth, 8,201 metres (26,906 feet), 28 km (17 mi) north-west of Everest and still on the border with China; while in the interior of Nepal, we find Dhaulagiri, the seventh, 8,167 m (26,795 ft); Manaslu, the eighth, 8,156 m (26,759 ft) high, and Annapurna, the ninth, 8,091 m (26,545 ft) high.
In the base camp of Everest, in the Khumbu glacier, 5,300 metres (17,400 ft) above sea level, only 450 mm (17.5 in) of rain or snow per year fall. Here the average temperature is around -18 °C (0 °F) in January, and -2 °C (28 °F) in July, while at the Everest's summit it's around -36 °C (-33 °F) in January and -18 °C (0 °F) in July. On the highest peaks of Nepal, terrible wind storms occur, especially in winter.


Nepal is too far from the sea to be directly hit by tropical cyclones, but the remains of cyclones affecting India, which usually come from the Bay of Bengal, can cause heavy rains in the Nepalese plains, as well as snow in the mountains, as happened on October 14, 2014, when heavy snowfalls produced avalanches in the Annapurna and Dhaulagiri areas, as a result of the approach of the remains of Cyclone Hudhud. To avoid these accidents, it is advisable to consult the weather forecasts and the official warnings, as well as to rely on local expert guides.
Cyclones typically occur from mid-April to early December, and most likely in May-June and October-November.


The best time to visit Nepal in its entirety runs from November to February, to avoid the summer monsoon, but also the heat on the plains, which is intense from March to October.
For visiting Kathmandu and especially for trekking in the mountains, you may choose spring and autumn, especially in March and April, and from mid-October to mid-November, the periods in which it is possible to avoid the winter cold as well as the mud due to summer rains. Autumn is the best period, because it is the least rainy and the atmosphere is particularly transparent, so that you can watch the snow-capped mountains at great distances.

In general, expeditions for Everest and the highest peaks are organized in two periods, from May 20 to June 5, and from October the 1st to the 20th, when the temperature on the summit of Everest is around -25/-27 °C (-13/-17 °F), and it's possible to take advantage of the only two benevolent periods between cloudiness and snowfalls which occur in summer, and wind storms which occur in winter. However, in the high mountains the weather can vary greatly depending on meteorological situation, so it's better to check the forecast for the following days, and in any case, to rely on expert guides.


In winter: in the plains, spring/autumn clothes, light for the day, jacket and sweater for the evening. In Kathmandu and Pokhara, spring/autumn clothes for the day, warm for the evening, jacket, hat, scarf, sunglasses, sunscreen. Above 2,000 metres (6,500 feet), warm winter clothes, down jacket, hiking shoes. At higher altitudes, outfit for the big cold, synthetic thermal long underwear, gloves, parka, hat, scarf.
In summer: for the plains, lightweight clothing of natural fibres, light raincoat or umbrella. In Kathmandu and Pokhara, light clothing, a sweatshirt for the evening, raincoat or umbrella. Above 2,000 metres (6,500 feet), spring/autumn clothes, sweater and jacket for the evening. At the highest altitudes, fleece, wind jacket, down jacket, hat, gloves, scarf. For overnight stays outdoors, sleeping bag, warm jacket.