The residents of the national capital woke up to heavy rains and rumbling of thunder on Sunday morning.

The rains brought the mercury down by several notches.

Waterlogging in low-lying areas and roads is likely to affect traffic movement, the India Meteorological Department (IMD) said in a forecast for Delhi-NCR issued at 6:30 am.

Till 5:30 am, the Safdarjung Observatory, which provides representative figures for the city, recorded 4.9 mm rainfall. The Palam weather station gauged3.8 mm precipitation.

Kuldeep Srivastava, head of the IMD's regional forecasting centre, said, "Moderate to isolated heavy rains were witnessed in parts of Delhi-NCR."

Earlier, the IMD had predicted isolated heavy to very heavy rainfall over parts of northwest India. It had said the "entire monsoon trough is most likely to shift northwards, closer to the foothills of the Himalayas during July 19-20".

Despite the early arrival of monsoon in Delhi, the rains have remained subdued.

According to the IMD, the Safdarjung Observatory has recorded 47.9 mm rainfall in July so far, which is 56 per cent less than the normal of 109.4 mm.

Palam and Lodhi Road weather stations have recorded 38 and 49 per cent less rains in July.

Srivastava said the fresh spell of rains will reduce the deficit to some extent.