Climate of Delhi
Delhi features a humid subtropical climate, with hot summers accompanied by frequent thunderstorms locally known as andhi, and cool winters that are characterized by dense fog. The city's rainfall pattern is heavily influenced by the summer monsoon entering in late June and continuing till mid-September, and western disturbances occurring from November to March.
Summer starts in early April and peaks in late May or early June, with average temperatures near although occasional heat waves can result in highs close to on some days and therefore higher apparent temperature. The monsoon starts in late June and lasts until mid-September, with about of rain. The average temperatures are around, although they can vary from around on rainy days to during dry spells. The monsoons recede in late September, and the post-monsoon season continues till late October, with average temperatures sliding from.
Winter starts in November and peaks in January, with average temperatures around. Although daytime temperatures are warm, Delhi's proximity to the Himalayas results in cold waves leading to lower apparent temperature due to wind chill. Delhi experiences heavy fog and haze during the winter season. In December, reduced visibility leads to disruption of road, air and rail traffic. Winter generally ends by the first week of March.
Extreme temperatures have ranged from.
Overview of seasonal distribution
- Spring: Mid-February to Early-April; warm days, cool nights, pleasant; low to moderate humidity; moderate precipitation
- Summer: Mid-April to Late June; hot to very hot; very low to moderate humidity; moderate precipitation
- Monsoon: July to Mid September; hot, pleasant during rains; high to very high humidity; heavy precipitation
- Autumn: Late September to November; warm days, cool nights, pleasant; low humidity; very low precipitation
- Winter: December to Early February; cool days, cold nights; moderate humidity; low precipitation
Seasons
Delhi lies in the landlocked Northern Plains of the Indian subcontinent. Its climate is greatly influenced by its proximity to the Himalayas and the Thar Desert, causing it to experience both weather extremes. Delhi has 5 distinct seasons, Summer, Rainy, Autumn, Winter and Spring. Broadly speaking, Delhi has long and scorching summers, sub-divided into dry summer and humid monsoon seasons, short and mildly cold winters, and two bouts of pleasant transition seasons. The two most important wind patterns influencing Delhi's climate are the Western Disturbance and the South-West Winds.Summer
Summer begins in mid April and continues till late June, with the heat peaking in late May and early June. It is characterized by extreme heat, low humidity, very hot winds and thunderstorms. Delhi's proximity to the Thar Desert results in hot, dry continental winds, called loo, at times blowing all across from the West Asian mainland, making the days feel hotter. These winds, blowing over from vast land stretches, are very hot and dry. Since the Western Disturbance depression moves eastward by this time of the year, there is no moisture-laden wind to increase humidity. The air therefore remains dry or very dry during the day. For most of its summer season, Delhi has a semi-arid climate. Coming from Spring, the city witnesses a spurt in day temperature around early April, whereas nights still remain pleasant. By the latter part of April or during early May, maximum temperatures exceed while the ambience remains very dry. Night temperatures cross the mark towards the latter part of April. May is Delhi's hottest month during which temperatures may reach or higher. This month is characterized by frequent thunderstorms, and can be severe and destructive when accompanied by strong winds, particularly under cumulonimbus formation. These storms also bring fine dust along by the hot winds arriving from the desert. They make the surroundings appear pale yellow, bring temperatures slightly down and are usually followed by heavy thundershowers. Post late-June, temperatures start falling slowly, while humidity shows a gradual rise.A visual characteristic of summer in Delhi is the summer bloom, particularly the blooming Bougainvillea, Amaltas, Gulmohar, Shireesh and Jacaranda trees, which are in full flower during peak summer in May.
Monsoon
Monsoon winds arrive in Delhi by either the end of June or the first week of July. The arrival of moisture-laden South-Western winds, travelling from the Arabian Sea marks the onset of the humid season in Delhi. This season is marked by high levels of humidity and high heat. Day temperatures drop below as humidity suddenly soars. July is marked by high heat and relatively less precipitation. This transition from scorching to sweltering heat between June and July makes the latter feel very uncomfortable. August is Delhi's wettest month. The heat is considerably reduced and it is relatively cooler for most of the month. There is dense cloud formation in the sky and at least a week of distinct, heavy rainfall. By September, the amount and frequency of precipitation drops, though humidity remains high. Towards the end of September, the moisture content in the air begins to fall and monsoon ends by early October. In India, the rainy season is referred to as "Rituraani", meaning the Queen of Seasons.Autumn
The end of the monsoon marks the arrival of a transition season. Autumn arrives by early or mid-October and is marked by a very dry ambience, warm days and pleasant nights. Maximum temperatures drop below by late October and there is a gradual fall in average temperature. The minimum temperature drops below. During Autumn, the wind direction begins changing from South-Westerly to North-Westerly. In recent decades, Delhi has seen a hazardous increase in air pollution levels and toxic smog for several weeks between late October and the end of November caused by stubble burning by farmers in the Indian states lying north of Delhi for fresh sowing at this time of the year, which is exacerbated by the usually almost still air around this time that causes the pollutants to hang in Delhi's air for many days. Around late autumn, the variation between morning and afternoon temperatures in a day becomes considerable, and can often be more than 20 °C, with minimum dropping to under and maximum still hovering slightly under. This season ends in early December.Winter
Winter arrives in Delhi by early December. Minimum temperatures gradually enter single digits by this time of the year, while days are cool. Though usually not very cold initially, December suddenly becomes cold in the latter half, as chilly north-western winds from the Himalayas begin sweeping the Northern Plains. These cold waves are caused by a depression created by Western Disturbance, which bring cloud cover and winter rains to the Plains, and add to snowfall in the North-Western Indian subcontinent. By early January, when winter peaks in Delhi, the minimum temperatures plunge to the vicinity of, though very rarely entering the negative scale. Maximum temperatures, too may drop down into single digits and always stay under. When the minimum temperature ventures very close to the mark, Delhi witnesses frost. Snow is a practical impossibility for Delhi due to very dry nature of its winter- the coldest conditions happen under clear skies when icy winds rush in from the Himalayas, and a cloud cover rather warms the city by trapping heat, thereby junking any possibility of snow. Delhi's winter is marked by very dense fog, which dramatically reduces visibility and makes days colder by cutting off sunlight. In the opposite scenario, cold north-westerly winds from the upper reaches of Himalayas blowing across the city make the days feel colder, despite any sunshine and the nights further cold. Post-mid-January, average temperatures begin to rise very gradually, though the rise is almost contained by the cold north-western winds which result due to very heavy snowfall that occurs in the Himalayas during this part of the month. It may rain towards the end of January and the precipitation is usually accompanied by hail, resulting in slight increase in minimum temperatures due to cloud cover. Maximum temperatures again cross and days become pleasant.By mid-February or somewhat beyond, minimum temperatures cross the mark and days start getting warmer gradually, marking the end of winter.
Delhi can sometimes have a prolonged season of chill, extending into March.