The southwest monsoon on Monday entered east Uttar Pradesh and is surging westward along the Gangetic Plains towards Delhi, weather officials said.
Pre-monsoon thunderstorm activity in Delhi and nearby areas may continue for the next two days, Dr R D Singh from the Indian Meteorological Department's Delhi office said.
The monsoon is expected to reach Delhi around June 29, which is the normal date.
Delhi has already recorded 91mm rainfall so far, which is more than the normal of 55mm for June.
"Moisture incursion from the Bay of Bengal branch of the monsoon is leading to pre-monsoon showers in Delhi, Punjab, Haryana, west Uttar Pradesh and Uttaranchal," Singh said.
The Arabian Sea branch of the monsoon has become sluggish and has not moved beyond Rajasthan, but the Bay of Bengal branch is active.
Officials said the southwest monsoon had entered eastern Uttar Pradesh and moderate to heavy rainfall was being recorded in many parts, including eastern Madhya Pradesh and Bihar.
The monsoon has covered Chhattisgarh, Jharkhand, Bihar and several parts of Maharashtra, western UP and MP.
Met officials said rainfall activity over UP and MP is likely to enhance in the next 48 hours.
Till last week, the country had recorded a 22 per cent deficiency in rainfall.