Nepal Weather & Climate Normals (1991–2020): Seasons & Monsoon Hub

When meteorologists describe 'normal' Nepal weather, they mean the climatological averages for the 30-year reference period 1991–2020 (roughly BS 2047–2077). Nepal's Department of Hydrology and Meteorology (DHM), the government agency under the Ministry of Energy, Water Resources and Irrigation responsible for all official weather and climate data, computes these normals from its national station network and uses them as the baseline in every bulletin: a month is called 'above normal' or 'below normal' relative to the 1991–2020 average. This page is a hub for those normals — the long-term averages that tell you what Nepal's weather is usually like — and is deliberately separate from pages on climate change, which cover how those averages are shifting.

Averaged across DHM's all-Nepal station network, the 1991–2020 seasonal precipitation normals sum to roughly 1,700 mm per year (winter 58.5 mm, pre-monsoon 219.0 mm, monsoon 1,369.1 mm and post-monsoon 64.0 mm). Commonly cited national averages range from about 1,500 mm to 1,600 mm depending on the dataset and station mix, but every dataset agrees on the headline fact: close to 80 percent of Nepal's annual rain falls in the four monsoon months of June to September.

Temperature cannot be summarised in a single national number, because Nepal climbs from about 60 m above sea level in the Tarai (at Kechana Kalan, Jhapa) to 8,848.86 m at Sagarmatha (Mount Everest) within about 200 km. DHM's mapping shows average annual maximum temperatures above 30°C across the southern plains but below 9°C in the high northern districts. As a rule of thumb, temperature falls roughly 6°C for every 1,000 m of elevation gained, so a single day can be sweltering in Chitwan, mild in Kathmandu and freezing at Everest Base Camp.

For weather analysis, DHM divides the year into four meteorological seasons: winter (December–February), pre-monsoon (March–May), monsoon (June–September) and post-monsoon (October–November). Each has a distinct character. Winter is dry and cool, fed only by occasional westerly disturbances that bring Himalayan snow and Tarai fog. Pre-monsoon is hot, hazy and thundery, with afternoon storms and the year's highest temperatures in May and early June. The monsoon is warm, humid and wet almost everywhere. Post-monsoon is the short, crisp transition famous for the clearest mountain views of the year.

Using the 1991–2020 normals, the monsoon contributes about 80 percent of all-Nepal annual precipitation, the pre-monsoon about 13 percent, and the post-monsoon and winter only about 3–4 percent each. Winter's national normal of just 58.5 mm explains why a failed winter westerly season — as in winter 2023–24 (BS 2080), when Nepal received only 19.8 percent of normal winter rain — quickly translates into drought stress for winter wheat and forest fires in spring.

Nepali tradition counts six seasons (chha ritu) rather than four, pairing the twelve Bikram Sambat (BS) months two by two: Basanta (spring, roughly Chaitra–Baisakh, mid-March to mid-May), Grishma (early summer, Jestha–Ashar, mid-May to mid-July), Barsha (the rainy season, Shrawan–Bhadra, mid-July to mid-September), Sharad (autumn, Ashwin–Kartik, mid-September to mid-November), Hemanta (pre-winter, Mangsir–Poush, mid-November to mid-January) and Shishir (winter, Magh–Falgun, mid-January to mid-March). Both framings are correct for different purposes: DHM's four seasons match the physics of the monsoon, while the six ritu structure festivals, almanacs and farming lore.

According to DHM, the normal (1991–2020 era) monsoon onset date for Nepal is 13 June, when the southwest monsoon current enters the country from the east, and the normal withdrawal date is 2 October, giving a normal monsoon duration of 112 days. The monsoon always arrives in eastern Nepal first — Koshi Province typically a few days before Kathmandu, and the far-western Tarai up to a week or more later — and it withdraws in the reverse direction, leaving the east last. In BS calendar terms, onset falls at the very end of Jestha or start of Ashar, which is why Ashar 15 (late June), the national paddy-planting day, sits squarely in the first flush of monsoon rain.

Actual dates swing widely around the normal. In DHM's record since 1968, the earliest onset was 31 May 1996 and the latest 27 June 1982; the earliest withdrawal was 2 September 1995 and the latest 19 October 2013. The shortest monsoon lasted just 73 days (1979) and the longest 130 days (2008). Recent seasons illustrate the spread: in 2024 (BS 2081) the monsoon entered on 10 June and withdrew on 12 October — 125 days, 13 days longer than normal — while in 2025 (BS 2082) it arrived on 29 May, a full 15 days early and among the earliest onsets on record.

For planning purposes, treat mid-June to early October as monsoon season, with July and August as the wettest, cloudiest core. DHM issues an official onset declaration and a seasonal outlook each year around late May or early June; trekkers, farmers and event planners should check the current bulletin rather than assume the normal dates, since a two-week deviation in either direction is entirely ordinary.

Nepal's rainfall map is dramatically uneven. Moist monsoon air slams into the first big mountain walls it meets, so the southern flanks of the Annapurna and other front ranges are drenched while the trans-Himalayan valleys behind them sit in rain shadow. Lumle in Kaski district, above Pokhara, is consistently Nepal's wettest station — it recorded the country's highest annual total of 4,572.7 mm in 2024 and averages well above 5,000 mm in many years — and the Pokhara valley itself averages around 3,345 mm a year, more than double Kathmandu. At the other extreme, Jomsom in Mustang, barely 50 km north of Lumle across the Annapurna massif, recorded just 337.6 mm in 2024, and upper Mustang and Dolpo average under 300 mm — a cold semi-desert.

The east–west gradient matters too: eastern Nepal generally receives more rain than the far west because it meets the Bay of Bengal monsoon branch first, while winter precipitation shows the opposite pattern, with westerly disturbances favouring Sudurpashchim and Karnali. Kathmandu Valley's annual normal is on the order of 1,400–1,500 mm, concentrated overwhelmingly in June–September.

Monsoon rain also delivers Nepal's most destructive weather. The national 24-hour rainfall record was shattered on 8 July 2024, when Dodhara station in Kanchanpur district measured 624.0 mm in a day, surpassing the previous record of 516.2 mm set at Hetauda on 13 August 2017. In the same year, 49 DHM stations broke their all-time 24-hour rainfall records — a reminder that while the normals describe the average year, individual monsoon seasons increasingly produce extremes, a trend examined in detail on our climate-change pages.

Nepal's temperatures are governed far more by elevation than by latitude. The Tarai plains (below about 300 m) are subtropical: summer maxima routinely exceed 40°C in the western Tarai before the monsoon breaks — Tikapur in Kailali touched 45.2°C on 30 May 2024 — while winter mornings dip to 5–10°C under fog. The mid-hills (roughly 1,000–2,000 m), including Kathmandu and Pokhara, are temperate: Nepal Tourism Board figures give Kathmandu typical summer highs/lows of about 28°C/20°C and winter values of about 19°C/3°C, with Pokhara a degree or two warmer. Above 3,000 m, summers are cool and winters severe; above roughly 5,000 m lies the nival zone of permanent snow and ice where no month is frost-free.

This vertical stacking means Nepal contains almost every climate type on Earth — tropical and subtropical in the lowlands, temperate in the mid-hills, subalpine and alpine in the high valleys, and arctic-like conditions on the high peaks — within a country averaging under 200 km north to south. For travellers the practical rule is to plan by elevation, not by season alone: December is pleasantly mild in Chitwan (winter highs around 24°C) at the same time it is dangerously cold above 4,000 m.

Interannual variability around the temperature normals is now consistently warm-side. DHM's State of the Climate of Nepal 2024 reports that 2024 recorded the country's highest average minimum temperature since 1981, with 50 days on which some station exceeded 40°C and Tarai heatwaves lasting 5 to 17 consecutive days between April and June. Those trends and their causes are covered on the dedicated climate-change pages; this hub keeps to the baseline averages.

The climate normals give a clear answer to the perennial question of the best time to visit Nepal: autumn (October–November) and spring (March–April) are the prime windows. Autumn, immediately after the normal 2 October monsoon withdrawal, combines the year's clearest mountain skies with mild temperatures and coincides with the great festivals of Dashain and Tihar — it is the peak trekking season. Spring offers warm days, blooming rhododendron forests on the trekking routes and the main Everest-climbing window, at the cost of increasing haze and pre-monsoon thunderstorms as May approaches.

The other seasons have real uses. Winter (December–February) is dry and sunny with superb visibility — excellent for the Tarai, Kathmandu Valley sightseeing, wildlife safaris in Chitwan and Bardiya and low-elevation treks — but high passes are snowbound and nights above 3,000 m are bitter. The monsoon (June–September) brings daily rain, leeches, cloud-hidden peaks and landslide-prone highways to most of the country, yet it is precisely the season to visit the rain-shadow districts: Upper Mustang, Dolpo and the Manang side of the Annapurnas stay relatively dry and green when everywhere else is soaked.

Whatever the month, remember that the normals are averages, not guarantees. Monsoon onset has ranged from 31 May to 27 June and withdrawal from early September to mid-October, and individual weeks in any season can defy the pattern. For fixed-date plans — a trek, a wedding, a paddy transplanting schedule — check DHM's current forecasts and seasonal outlook against the baseline this page provides.

This page anchors amarnepal.com's weather-normals coverage. From here you can drill down to per-city and per-region climate normal pages — Kathmandu, Pokhara, Chitwan (Bharatpur), Biratnagar, Nepalgunj, Jomsom and other stations — each presenting DHM-based monthly temperature and rainfall normals, as those pages are published. Related reference pages already on the site include the Nepali months and six-seasons (ritu) reference hub, the flood early-warning and river danger levels directory, and the air-quality explainer; Nepal's warming trends, glacier retreat and climate projections live on the separate climate-change pages.

All figures on this page trace to primary sources: DHM's State of the Climate of Nepal reports, its monsoon onset and withdrawal bulletins, and its published 1991–2020 climatological normals, supplemented by Nepal Tourism Board climate summaries for visitor-facing temperature tables. DHM updates the onset/withdrawal record and the State of the Climate report annually, and climate normals themselves are recalculated once a decade under World Meteorological Organization (WMO) practice — the 1991–2020 set replaced the 1981–2010 set and will remain the official baseline until a 2001–2030 update. Where figures on this page are dataset-dependent (such as the national average rainfall), the range is stated rather than a false single number.