Question: When is monsoon season in the city where Northern Railway is headquartered?

full_context: Document 1: Delhi: Delhi features a dry-winter humid subtropical climate (Köppen Cwa) bordering a hot semi-arid climate (Köppen BSh). The warm season lasts from 21 March to 15 June with an average daily high temperature above 39 °C (102 °F). The hottest day of the year is 22 May, with an average high of 40 °C (104 °F) and low of 28 °C (82 °F). The cold season lasts from 26 November to 9 February with an average daily high temperature below 20 °C (68 °F). The coldest day of the year is 4 January, with an average low of 2 °C (36 °F) and high of 14 °C (57 °F). In early March, the wind direction changes from north-westerly to south-westerly. From April to October the weather is hot. The monsoon arrives at the end of June, along with an increase in humidity. The brief, mild winter starts in late November, peaks in January and heavy fog often occurs.Temperatures in Delhi usually range from 2 to 47 °C (35.6 to 116.6 °F), with the lowest and highest temperatures ever recorded being −2.2 and 48.4 °C (28.0 and 119.1 °F), respectively. The annual mean temperature is 25 °C (77 °F); monthly mean temperatures range from 13 to 32 °C (55 to 90 °F). The highest temperature recorded in July was 45 °C (113 °F) in 1931. The average annual rainfall is approximately 886 mm (34.9 in), most of which falls during the monsoon in July and August. The average date of the advent of monsoon winds in Delhi is 29 June.
Document 2: Climate of India: The Climate of India comprises a wide range of weather conditions across a vast geographic scale and varied topography, making generalisations difficult. Based on the Köppen system, India hosts six major climatic subtypes, ranging from arid desert in the west, alpine tundra and glaciers in the north, and humid tropical regions supporting rainforests in the southwest and the island territories. Many regions have starkly different microclimates. The country's meteorological department follows the international standard of four climatological seasons with some local adjustments: winter (December, January and February), summer (March, April and May), a monsoon rainy season (June to September), and a post-monsoon period (October to November).
Document 3: Hyderabad: The most commonly used forms of medium distance transport in Hyderabad include government owned services such as light railways and buses, as well as privately operated taxis and auto rickshaws. Bus services operate from the Mahatma Gandhi Bus Station in the city centre and carry over 130 million passengers daily across the entire network.:76 Hyderabad's light rail transportation system, the Multi-Modal Transport System (MMTS), is a three line suburban rail service used by over 160,000 passengers daily. Complementing these government services are minibus routes operated by Setwin (Society for Employment Promotion & Training in Twin Cities). Intercity rail services also operate from Hyderabad; the main, and largest, station is Secunderabad Railway Station, which serves as Indian Railways' South Central Railway zone headquarters and a hub for both buses and MMTS light rail services connecting Secunderabad and Hyderabad. Other major railway stations in Hyderabad are Hyderabad Deccan Station, Kachiguda Railway Station, Begumpet Railway Station, Malkajgiri Railway Station and Lingampally Railway Station. The Hyderabad Metro, a new rapid transit system, is to be added to the existing public transport infrastructure and is scheduled to operate three lines by 2015.
Document 4: New Delhi: The Delhi Metro is a rapid transit system serving New Delhi, Delhi, Gurgaon, Faridabad, Noida, and Ghaziabad in the National Capital Region of India. Delhi Metro is the world's 12th largest metro system in terms of length. Delhi Metro was India's first modern public transportation system, which had revolutionised travel by providing a fast, reliable, safe, and comfortable means of transport. The network consists of six lines with a total length of 189.63 kilometres (117.83 miles) with 142 stations, of which 35 are underground, five are at-grade, and the remainder are elevated. All stations have escalators, elevators, and tactile tiles to guide the visually impaired from station entrances to trains. It has a combination of elevated, at-grade, and underground lines, and uses both broad gauge and standard gauge rolling stock. Four types of rolling stock are used: Mitsubishi-ROTEM Broad gauge, Bombardier MOVIA, Mitsubishi-ROTEM Standard gauge, and CAF Beasain Standard gauge.
Document 5: Majnu-ka-tilla: The area lies on a stretch of the National Highway 1, which is part of the historic Grand Trunk Road and the Outer Ring Road of Delhi. It is at a walkable distance from ISBT Kashmere Gate. It is approachable through the Kashmeri Gate station of the Delhi Metro, lies on both the Red (Dilshad Garden - Rithala) and Yellow Lines (Samaypur Badli - HUDA City Centre). It is a transfer station between the Red Line on the highest upper level and the Yellow Line on the lowest level. The Vidhan Sabha metro station is 1.5 km away.
Document 6: Hyderabad: Hyderabad has a tropical wet and dry climate (Köppen Aw) bordering on a hot semi-arid climate (Köppen BSh). The annual mean temperature is 26.6 °C (79.9 °F); monthly mean temperatures are 21–33 °C (70–91 °F). Summers (March–June) are hot and humid, with average highs in the mid-to-high 30s Celsius; maximum temperatures often exceed 40 °C (104 °F) between April and June. The coolest temperatures occur in December and January, when the lowest temperature occasionally dips to 10 °C (50 °F). May is the hottest month, when daily temperatures range from 26 to 39 °C (79–102 °F); December, the coldest, has temperatures varying from 14.5 to 28 °C (57–82 °F).
Document 7: New Delhi metro station: New Delhi is a station on the Yellow Line of the Delhi Metro. It is within walking distance from the Indian Railways New Delhi station. It is on the Ajmeri Gate (Platform Number 16) side of the New Delhi Railway Station.
Document 8: Climate of Islamabad: The climate of Islamabad has a humid subtropical climate (Köppen climate classifion, with five seasons: Winter (Nov − Feb), Spring (March − April), Summer (May − June), Rainy Monsoon (July − August) and Autumn (September − October). The hottest month is June, where average highs routinely exceed 38 ° C (100.4 ° F). The wettest month is July, with heavy rainfall and evening thunderstorms with the possibility of cloudburst. The coolest month is January, with temperatures variable by location. In Islamabad, temperatures vary from cold to mild, routinely dropping below zero. In the hills there is sparse snowfall. The weather ranges from a minimum of − 3.9 ° C (25.0 ° F) in January to a maximum of 46.1 ° C (115.0 ° F) in June. The average low is 2 ° C (35.6 ° F) in January, while the average high is 38.1 ° C (100.6 ° F) in June. The highest temperature recorded was 46.5 ° C (115.7 ° F) in June, while the lowest temperature was − 4 ° C (24.8 ° F) in January. On 23 July 2001, Islamabad received a record breaking 620 millimetres (24 in) of rain fell in just 10 hours. It was the heaviest rainfall in 24 hours in Islamabad and at any locality in Pakistan during the past 100 years. Following is the weather observed over Islamabad Airport, which is actually located in Rawalpindi.
Document 9: New Delhi: New Delhi is a major junction in the Indian railway network and is the headquarters of the Northern Railway. The five main railway stations are New Delhi railway station, Old Delhi, Nizamuddin Railway Station, Anand Vihar Railway Terminal and Sarai Rohilla. The Delhi Metro, a mass rapid transit system built and operated by Delhi Metro Rail Corporation (DMRC), serves many parts of Delhi and the neighbouring cities Faridabad, Gurgaon, Noida and Ghaziabad. As of August 2011, the metro consists of six operational lines with a total length of 189 km (117 mi) and 146 stations, and several other lines are under construction. It carries millions of passengers every day. In addition to the Delhi Metro, a suburban railway, the Delhi Suburban Railway exists.
Document 10: Hazrat Nizamuddin railway station: Nizamuddin हज़रत निज़ामुद्दीन Rapid transit, Light rail, Commuter rail & Regional rail station Location New Delhi, Delhi India 28 ° 35 ′ 21 ''N 77 ° 15 ′ 15'' E ﻿ / ﻿ 28.58917 ° N 77.25417 ° E ﻿ / 28.58917; 77.25417 Elevation 206.7 metres (678 ft) Platforms 7 Construction Structure type Standard (on ground station) Parking Yes Other information Status Functioning Station code NZM Zone (s) Northern Railway zone Division (s) Delhi Electrified Yes Traffic Passengers (Daily) 360,000 + Location Nizamuddin Location within Delhi
Document 11: New Delhi: New Delhi has one of India's largest bus transport systems. Buses are operated by the state-owned Delhi Transport Corporation (DTC), which owns largest fleet of compressed natural gas (CNG)-fueled buses in the world. Personal vehicles especially cars also form a major chunk of vehicles plying on New Delhi roads. New Delhi has the highest number of registered cars compared to any other metropolitan city in India. Taxis and Auto Rickshaws also ply on New Delhi roads in large numbers. New Delhi has one of the highest road density in India.
Document 12: Urban rail transit in India: There are currently 11 operational rapid transit (also called 'metro') systems in ten cities in India. As of November 2017, India has 425 kilometres (264 miles) of operational metro lines and 347 stations. A further 500 + km of lines are under construction. Metro rail lines in India are composed of mainly standard gauge. Projects like the Kolkata Metro and Delhi Metro used broad gauge for their earliest lines but all new projects in India are on standard gauge as rolling stock imported is of standard gauge.
Document 13: New Delhi: The climate of New Delhi is a monsoon-influenced humid subtropical climate (Köppen Cwa) with high variation between summer and winter in terms of both temperature and rainfall. The temperature varies from 46 °C (115 °F) in summers to around 0 °C (32 °F) in winters. The area's version of a humid subtropical climate is noticeably different from many other cities with this climate classification in that it features long and very hot summers, relatively dry and mild winters, a monsoonal period, and dust storms. Summers are long, extending from early April to October, with the monsoon season occurring in the middle of the summer. Winter starts in November and peaks in January. The annual mean temperature is around 25 °C (77 °F); monthly daily mean temperatures range from approximately 14 to 34 °C (57 to 93 °F). New Delhi's highest temperature ever recorded is 49.1 °C (120.4 °F) while the lowest temperature ever recorded is −3.2 °C (26.2 °F). Those for Delhi metropolis stand at 49.9 °C (121.8 °F) and −3.2 °C (26.2 °F) respectively. The average annual rainfall is 784 millimetres (30.9 in), most of which is during the monsoons in July and August.
Document 14: Kathmandu: The city generally has a climate with warm days followed by cool nights and mornings. Unpredictable weather is expected, given that temperatures can drop to 1 °C (34 °F) or less during the winter. During a 2013 cold front, the winter temperatures of Kathmandu dropped to −4 °C (25 °F), and the lowest temperature was recorded on January 10, 2013, at −9.2 °C (15.4 °F). Rainfall is mostly monsoon-based (about 65% of the total concentrated during the monsoon months of June to August), and decreases substantially (100 to 200 cm (39 to 79 in)) from eastern Nepal to western Nepal. Rainfall has been recorded at about 1,400 millimetres (55.1 in) for the Kathmandu valley, and averages 1,407 millimetres (55.4 in) for the city of Kathmandu. On average humidity is 75%. The chart below is based on data from the Nepal Bureau of Standards & Meteorology, "Weather Meteorology" for 2005. The chart provides minimum and maximum temperatures during each month. The annual amount of precipitation was 1,124 millimetres (44.3 in) for 2005, as per monthly data included in the table above. The decade of 2000-2010 saw highly variable and unprecedented precipitation anomalies in Kathmandu. This was mostly due to the annual variation of the southwest monsoon.[citation needed] For example, 2003 was the wettest year ever in Kathmandu, totalling over 2,900 mm (114 in) of precipitation due to an exceptionally strong monsoon season. In contrast, 2001 recorded only 356 mm (14 in) of precipitation due to an extraordinarily weak monsoon season.
Document 15: Nanjing: Nanjing has a humid subtropical climate (Köppen Cfa) and is under the influence of the East Asian monsoon. The four seasons are distinct, with damp conditions seen throughout the year, very hot and muggy summers, cold, damp winters, and in between, spring and autumn are of reasonable length. Along with Chongqing and Wuhan, Nanjing is traditionally referred to as one of the "Three Furnacelike Cities" along the Yangtze River (长江流域三大火炉) for the perennially high temperatures in the summertime. However, the time from mid-June to the end of July is the plum blossom blooming season in which the meiyu (rainy season of East Asia; literally "plum rain") occurs, during which the city experiences a period of mild rain as well as dampness. Typhoons are uncommon but possible in the late stages of summer and early part of autumn. The annual mean temperature is around 15.46 °C (59.8 °F), with the monthly 24-hour average temperature ranging from 2.4 °C (36.3 °F) in January to 27.8 °C (82.0 °F) in July. Extremes since 1951 have ranged from −14.0 °C (7 °F) on 6 January 1955 to 40.7 °C (105 °F) on 22 August 1959. On average precipitation falls 115 days out of the year, and the average annual rainfall is 1,062 millimetres (42 in). With monthly percent possible sunshine ranging from 37 percent in March to 52 percent in August, the city receives 1,983 hours of bright sunshine annually.
ground_truth: the middle of the summer
sub_queries: What Indian city is the headquarters of the Northern Railway? Answer: New Delhi
When does the monsoon season occur in New Delhi ? Answer: the middle of the summer