Nepal's climate is set by two things: the South Asian monsoon, which brings most of the year's rain between June and September, and altitude. Within a country only 150–250 km wide, the land climbs from 59 m in the Terai plains to 8,848.86 m on Mount Everest, giving Nepal eight climate zones, from tropical lowlands to permanent snow. In the Terai, around Biratnagar and Nepalgunj, summers are hot and humid, with May highs of 34–38 °C. Kathmandu, at 1,337 m in the middle hills, is mild: January highs average 19.2 °C and July lows 20.3 °C. Above about 5,000 m lies the nival zone of permanent snow and ice. Rainfall ranges from about 160 mm a year in rain-shadow valleys north of the Himalaya to more than 5,500 mm on the windward slopes near Pokhara.
Nepal is usually divided into three east–west belts. The Terai, the northern edge of the Gangetic Plain, covers 17% of the country. The hill region, or Pahad, which includes the Kathmandu and Pokhara valleys, covers 68%. The Himal, the snow-bearing mountain belt, covers the remaining 15%. Each belt has its own climate, but the same calendar runs through all three: a long dry season from October to May, and a wet season that usually arrives in mid-June. Its arrival can shift by up to a month.
June to September: the monsoon that brings nearly four-fifths of Kathmandu's rain
The monsoon happens because Inner Asia heats up in summer. A low-pressure zone forms over the continent and pulls in moist air from the Indian Ocean. The air reaches Nepal from the Bay of Bengal in the south-east, which is why the east gets wetter summers than the west. When the air meets the hills, it rises, cools and drops its moisture. Our explainer on how monsoons work covers the large-scale mechanism. Kathmandu's record shows how sharp the resulting seasons are.
In the 1991–2020 World Meteorological Organization normals for Tribhuvan International Airport, Kathmandu receives about 1,502 mm of precipitation a year. Of that, 1,176 mm, or 78%, falls from June to September. July is the wettest month at 384.1 mm, with rain on about 23 days. November gets only 6.4 mm, and December 7.8 mm. Sunshine follows the clouds: Kathmandu averages 244 hours of sun in May but only 130 hours in July.
Temperatures change little through the wet months. Kathmandu's average highs stay between 28.6 °C and 29.5 °C from June to September, and the clouds keep nights warm, with lows of 19–20 °C. The monsoon is felt more in the humidity, which averages 81–83% in July and August, and in its effects on travel. Unpaved roads wash out, trails turn to mud, and low cloud makes mountain flights harder. The rains ease in September and usually end by mid-October.
Pokhara, Biratnagar and Jomsom: where the rain lands
Annual rainfall in Nepal depends more on where the hills face the moist air than on latitude. In broad terms it falls from east to west: about 2,500 mm a year in the east, about 1,400 mm around Kathmandu and about 1,000 mm in the west. Local terrain then changes those averages sharply.
Pokhara, at 827 m, is the clearest case. Within 30 km of the city, the land rises from about 1,000 m to 7,500 m in the Annapurna range. That forces the monsoon air upward and makes it drop its rain. Pokhara Airport records about 3,868 mm a year, with 941 mm in July alone. Lumle, about 40 km from the city centre, gets more than 5,600 mm a year, the highest rainfall in Nepal. Behind the same mountains the pattern reverses. Jomsom, at 2,741 m in the Kali Gandaki valley of Mustang, averages only about 292 mm a year, and its wettest month, July, brings just 46.8 mm.
In the Terai, the gap between east and west is easier to see. Biratnagar, in the far east, averages about 1,758 mm a year, with 475.6 mm in July. Nepalgunj, in the mid-west lowlands, averages about 1,475 mm, and 86% of it falls from June to September. That makes western farming especially dependent on the timing of the monsoon.
In the Khumbu, the monsoon still dominates even at high altitude. Namche Bazaar, at 3,450 m, receives about 952 mm a year, and roughly three-quarters of it falls from June to September. Its winter months are not completely dry, though: January brings about 43 mm, more than any other month from November to May. When the rains failed in the past, the result was drought and famine. Rains well above normal still bring floods and landslides.
26–29 September 2024: the storm that flooded the Bagmati
The 2024 season showed how much damage a heavy monsoon can still do. A low-pressure system stalled over India and the Bay of Bengal. From 26 September it brought heavy rain across most of Nepal, with the eastern and south-eastern districts hit hardest. In the 24 hours from the morning of 28 September to the morning of 29 September, the Kathmandu Valley received between 240 mm and 322.2 mm. That was the capital's largest recorded rainfall since at least 1970, roughly what the city normally receives in the whole of June.
The Bagmati River rose two metres above its safe level and flooded large parts of southern Kathmandu. The government reported at least 224 deaths in late September, including at least 37 in Kathmandu itself. On 27 September all domestic flights out of Kathmandu were cancelled, and schools and universities closed for three days. Earlier that summer, on 16 August 2024, two glacial lakes burst above the village of Thame in the Everest region. Temperatures there had been rising since 9 August and reached 15 °C on the day of the flood. It was a reminder that in the Himal, rising heat can cause floods as well as rain.
October to February: Dashain skies, valley frost and Himalayan snow
After the monsoon, the weather turns cool, clear and dry. Nepal's two largest Hindu festivals, Dashain and Tihar, fall about a month apart in this post-monsoon season, once the harvest is in. From about December, the winter monsoon, a strong north-easterly flow, brings occasional short showers to the lowlands and snow to the high mountains. The Himalaya also blocks cold air from Inner Asia, so southern Nepal has warmer winters than it otherwise would.
The valleys can still be cold at night. Kathmandu's January averages run from a high of 19.2 °C to a low of 2.8 °C, and the city's lowest recorded temperature is −3.5 °C, set in 1978. Snow in the city itself is rare enough that the falls of 1945 and 2007 are still remembered. Pokhara is milder, with a record low of 0.5 °C on 13 January 2012. Even the Terai can turn chilly under winter fog. Nepalgunj reached −0.3 °C on 9 January 2013, its lowest on record.
Higher up, winter is much harsher. Namche Bazaar, the Sherpa town at 3,450 m on the trail to Everest, averages −8.5 °C on January nights, though January days still reach about 6.9 °C. Jomsom, in Mustang, falls to about −1.9 °C on January nights. On Everest itself, every month averages well below freezing. The climate is classed as ice cap (Köppen EF), and the summit is exposed to the jet stream. Winds there commonly reach 160 km/h, and a wind speed of 280 km/h was recorded at the summit in February 2004. Our Mount Everest guide explains why climbers aim for May, when the jet stream moves north just before the monsoon arrives.
March to May: Terai heat before the rains
Spring is the hottest and most stressful season in the lowlands. By April and May the long dry season has drained the soil, and afternoon temperatures below about 1,200 m can top 40 °C. The coarse gravels of the Chure, or Siwalik, hills hold little water, so many slopes there carry drought-tolerant scrub forest. Before the monsoon arrives, thunderstorms build. Kathmandu's May rainfall of 128.8 mm is about twice its April total, and that early rain fills the seedbeds for the rice crop.
The far west of the Terai gets the worst of the heat. In the WMO table for Dhangadhi, near the Indian border, the record for 1975–2017 is 46.4 °C, set in June. Nepalgunj often goes above 40 °C between April and June. Pokhara's highest reading, 38.5 °C, came on 4 May 2013, and Kathmandu's record of 36.6 °C also falls in May. In all of these places the heat ends when the monsoon arrives in June and clouds cover the sky.
Altitude shapes Nepal's farming as much as the seasons do. The lower tropical zone, below 300 m, takes in almost all of the Outer Terai and grows the best mangoes, papayas and bananas. The subtropical zone, from 1,000 to 2,000 m, covers 22% of the country and has up to 53 frost days a year. It grows rice, maize, millet and citrus. Between 2,000 and 3,000 m, the temperate zone can have up to 153 frost days. The subalpine zone, from 3,000 to 4,000 m, can have up to 229, and above 5,000 m nobody lives. To see how these belts fit with the rivers and ranges that create them, read our guide to Nepal's geography.