Heavy rain lashed Delhi and Mumbai on Sunday as monsoon arrived in both the cities on the same day — the first such occurrence since 1961.

According to the India Meteorological Department (IMD), the monsoon began two days earlier than usual in Delhi while its entry over Mumbai was delayed by two weeks.

Between Saturday night and Sunday evening, Delhi’s primary weather observatory at Safdarjung recorded 50.7 mm rainfall. While the minimum temperature was 23.1° Celsius, five degrees below normal, the maximum was 29° Celsius, eight degrees below normal.

The IMD has forecast moderate rain in the Capital on Monday followed by light rainfall till Thursday. This is expected to be followed by a few days of low rainfall. On Sunday, the maximum temperature is expected to be 30° Celsius.

Meanwhile, according to the IMD, active rainfall is expected across the country in the coming days as a cyclonic circulation in the east will move towards central India. This is likely to reduce the rainfall deficit for June which, currently, stands at 25 per cent.

So far in June, the country has received 91.8 mm rainfall against the normal expected rainfall of 126.9 mm. The IMD had predicted a 8 per cent deficit for June.

Delhi and Mumbai last witnessed the arrival of the monsoon on the same day on June 21, 1961. Based on data collected between 1961 and 2019, the normal onset of monsoon in Delhi has occurred on June 27.

Over the past few years, however, it has varied, with the Capital receiving its first monsoon showers last year on June 30. In 2021, Delhi’s monsoon onset was on July 13; and in the two years before that, it was marked on June 25 and July 5, respectively.

Kuldeep Srivastava, scientist at IMD said that while Delhi does not have predefined criteria to declare the onset of monsoons, conditions such as prevailing eastern winds, low-lying cloud cover and a forecast of 2-3 days of rain is read together to make the call.

For Kerala, though, the IMD has specific guidelines to declare the onset of monsoon: this includes the coverage of rain in 14 stations in the state and certain parameters for the depth and speed of wind as well as energy emitted by Earth.

Meanwhile, according to an IMD statement, conditions are ripe for the monsoon to enter Haryana and Punjab and also to cover the whole of Gujarat and Rajasthan in the next 48 hours.

On Sunday, the monsoon advanced in remaining parts of Maharashtra, besides Madhya Pradesh, Uttar Pradesh, Delhi, Gujarat, Rajasthan, Haryana, Uttarakhand, Himachal Pradesh, J&K and Ladakh today, the statement added.

The monsoon this year covered parts of Northwest India ahead of schedule but lagged behind in Central and West India.

According to senior IMD officials, this was because of the impact of Cyclone Biparjoy over the central and southern parts of the country.

IMD has forecast below normal rain for northwest India this year at around 92% of the normal.