Climate Zones of Nepal: Köppen Classification and Belt-by-Belt Guide

The climate of Nepal is defined by two forces: extreme altitude change and the South Asian summer monsoon. Within a north-south span of only about 150 to 250 kilometres, the land rises from roughly 60 metres above sea level in the southern Terai plains to 8,848.86 metres at the summit of Mount Everest (Sagarmatha). Because air temperature falls steadily with height, this vertical relief packs almost every major climate type on Earth into one small country, from hot and humid tropics to frozen polar conditions.

For everyday description, geographers group Nepal into a handful of climate zones that broadly follow elevation: tropical and subtropical lowlands, a cool temperate hill belt, cold high-mountain valleys, and a frigid alpine to nival (perpetual snow) zone in the high Himalaya. A separate, drier trans-Himalayan belt sits in the rain shadow north of the main range. These practical zones line up closely with Nepal's physiographic belts and with the more formal Köppen-Geiger climate classification.

The most rigorous modern map of Nepal's climate comes from Karki, Talchabhadel, Aalto and Baidya's 2016 (2072-73 BS) study 'New climatic classification of Nepal', published in Theoretical and Applied Climatology. Using 30 years of station data, they found that Nepal contains representatives of all five major Köppen climate groups, with a temperate, dry-winter, hot-summer type (Cwa) covering the largest share of the country.

The Köppen-Geiger classification is the world's most widely used climate scheme. It assigns each place a code of two or three letters. The first (capital) letter is the main group: A for tropical, B for arid (dry), C for temperate, D for cold (continental) and E for polar. The second letter describes the rainfall pattern (for example, 'w' means a dry winter, 's' a dry summer, 'f' no dry season). The third letter, where used, describes summer heat (a = hot, b = warm, c = cool). So 'Cwa' reads as temperate, with a dry winter and a hot summer.

Karki and colleagues built a high-resolution climate map of Nepal from long-term (1981-2010) data: monthly precipitation from 240 stations and mean air temperature from 74 stations, all maintained by the Department of Hydrology and Meteorology (DHM). When they applied the original Köppen-Geiger thresholds, the scheme failed to reproduce all five climate types actually observed on the ground; in particular, it could not identify a genuine tropical climate in the Terai.

To fix this, the authors slightly modified the system, lowering the boundary that separates tropical (A) from temperate (C) climates. The threshold for the coldest month's mean air temperature was changed from 18 degrees Celsius to 14.5 degrees Celsius. This adjustment lets the warm, monsoon-fed southern lowlands be classified as tropical, giving a more realistic picture of Nepal's climate than the unmodified global scheme.

Under the modified classification, Nepal's climate mosaic runs from tropical savanna in the far south to ice cap on the highest peaks. The single most common type is Cwa, a temperate climate with a dry winter and a hot summer, which dominates the low hills and much of the southern belt. The area coverage broadly tracks elevation, so the warmest types occupy the largest lowland areas and the coldest types cling to small high-altitude pockets.

The study reports that Cwa over the southern lowlands (below about 400 metres) covers roughly 30 percent of Nepal's total area, the single largest share. At the opposite extreme, Dwc (a cold climate with dry winter and cool summer) over the northern high mountains has the smallest coverage, around 0.5 percent. Between these extremes lie subtropical and temperate hill climates and, on the highest ground, the polar tundra (ET) and ice-cap (EF) types where the warmest month stays cold or below freezing.

Nepal is conventionally divided from south to north into five physiographic (landform) belts, and each carries a characteristic climate signature. Because temperature drops by roughly 6 to 6.5 degrees Celsius for every 1,000 metres of ascent, moving north across these belts is climatically similar to travelling from the tropics toward the poles. The belts therefore provide an intuitive bridge between Nepal's geography and its Köppen types.

The southern lowland Terai and the low Siwalik (Churia) foothills carry tropical to subtropical climates (Aw, Cwa). The Middle Mountains (Mahabharat Lekh and the hill valleys, including Kathmandu and Pokhara) are temperate (Cwa, Cwb). The High Mountains grade into cold and subalpine conditions (Cwc, Dwc), while the High Himal, above the permanent snow line, is polar tundra to ice cap (ET, EF). North of the main range, sheltered trans-Himalayan districts such as Mustang, Manang and Upper Dolpa form a cold, arid rain-shadow desert.

Alongside the Köppen scheme, Nepali sources often describe climate using altitudinal (vertical) zones, which are easy to relate to farming, forests and daily life. These bands are approximate and shift a little with aspect (sun-facing versus shaded slopes) and with east-to-west differences in rainfall, but they capture the broad pattern well.

In the tropical and subtropical lowlands and low hills, summers are hot and humid and frost is rare; this is Nepal's main belt for rice, sugarcane and citrus. The temperate hill zone has mild summers and cool, sometimes frosty winters, supporting maize, millet, vegetables and much of the country's population. Higher still, the subalpine and alpine zones have short, cool growing seasons suited to barley, potatoes, buckwheat and yak herding, while the nival zone above the snow line supports no cultivation.

The trans-Himalayan zone is a special case. Because the Himalaya block most monsoon moisture, districts north of the main range are cold high-altitude deserts that receive only a few hundred millimetres of precipitation a year, much of it as snow. This contrast between the wet, forested southern slopes and the dry northern valleys is one of the defining features of Nepal's climate.

Rainfall in Nepal is dominated by the summer monsoon. The four-month period from June to September delivers roughly 80 percent of the country's annual precipitation; in and around the Kathmandu Valley, for example, about 80 percent of the year's rain falls in these monsoon months. The DHM recognises four seasons: winter (December-February), pre-monsoon (March-May), monsoon (June-September) and post-monsoon (October-November).

Amounts vary enormously with location. Windward southern slopes that face the incoming monsoon, such as the Lumle-Pokhara area on the flank of the Annapurna range, are among the wettest places in the country and can receive well over 5,000 millimetres a year. By contrast, sheltered rain-shadow pockets in the trans-Himalaya (parts of Mustang and Manang) may get only a few hundred millimetres, in some spots as little as around 160 millimetres. There is also a broad east-to-west gradient: eastern Nepal, which the monsoon reaches first, is generally wetter than the far west.

Temperature likewise swings with altitude and season. The Terai can exceed 40 degrees Celsius in the pre-monsoon heat, while Kathmandu (about 1,300 metres) averages roughly 19 degrees Celsius annually and receives on the order of 1,450 millimetres of rain. High-mountain and Himalayan stations stay cold year-round, with the highest zones below freezing for most or all of the year.

A reliable climate map underpins much of Nepal's planning. Agriculture depends on matching crops to the right thermal and rainfall zone; forestry and biodiversity conservation rely on the same altitudinal gradients; and disaster risk work, from monsoon floods and landslides to Himalayan glacial-lake outburst floods, needs to know how rainfall and temperature vary across belts. The Köppen types give scientists a common language to compare Nepal with other mountain regions and to design weather-station networks.

The classification is also a baseline for tracking climate change. Follow-up research using the same framework has examined how Nepal's climate boundaries may shift upslope as the country warms, potentially expanding warmer zones and shrinking cold and nival areas. Because Nepal warms faster at higher elevations, these shifting boundaries have direct consequences for snow, glaciers, water supply and mountain ecosystems.

Readers should treat the specific figures here as durable but indicative. The Köppen results come from 1981-2010 data and a modified threshold designed for Nepal, and altitudinal zone limits vary between sources. For the latest seasonal outlooks, station records and monsoon summaries, the Department of Hydrology and Meteorology (DHM) is the authoritative Nepali source.