Delhi and the National Capital Region on Wednesday morning received pre-monsoon showers that brought down the maximum temperature by six degrees Celsius. The India Meteorological Department predicted heavy showers in isolated pockets on Wednesday and said the monsoon is likely to arrive on Thursday.

“The first two days of the week have seen light rains, the main rainfall activity will start in Delhi-NCR from Wednesday,” said Kuldeep Srivastava, senior scientist at the regional forecast centre in Delhi, according to the Hindustan Times.

The usual date for the onset of monsoon in Delhi is June 29. However, for the last two years it has arrived on July 2. “There is a western disturbance over Pakistan at the moment, it is expected to interact with monsoon system on June 27 and June 28 and bring heavy rainfall,” said DS Pai, senior scientist at India Meteorological Department, Pune.

Heavy downpours and thunderstorms are predicted over the weekend. The maximum temperature will be around 32 degrees Celsius while the minimum temperature will drop to 28 degrees Celsius during the rest of the week, reported NDTV.

Uttar Pradesh, Haryana, Chandigarh and Delhi have experienced heat wave conditions recently. “Due to overcast skies and cloudiness, the maximum temperatures in the Capital fell from 42 degrees Celsius on Monday to 34 degrees Celsius on Tuesday,” Mahesh Palawat, the chief meteorologist at Skymet Weather, told the Hindustan Times.

On Tuesday, pollution levels across Noida and Greater Noida also reduced considerably after a light drizzle. The air quality improved from “poor” to “moderate”. Officials said the pollution levels are expected to be low during monsoon, especially if the rainfall is consistent.