The nip is back in the air.

The minimum temperature of the city plummeted to 9.5°C on Friday morning from Thursday's 14.5°C, as westerly breeze started blowing after clouds dispersed. Weathermen claimed that the shivery condition could prevail for a couple of days.

'The cloud cover over the past two-three days got cleared last (Thursday) night, allowing the radiation from the earth's surface to escape to the upper layer of the atmosphere. This led to sudden drop in the night temperature. The minimum temperature is expected to drop further by a degree on Sunday and remain around 8.5°C on Saturday, and around 9°C,' said Ashish Sen, the director of Patna meteorological centre.

Deliberating on the expected wind speed, Sen said: 'The westerly wind was blowing at an average speed of 8-10kmph on Friday, leading to the wind-chill condition. The wind is coming from a western disturbance lying over western Himalayas. We expect such wind-chill condition would prevail over the next two days.'

The wind-chill condition is said to prevail on a wintry day when the wind speed and the level of moisture in the atmosphere are quite high. Weathermen claimed that the average level of moisture in the atmosphere on Friday was around 60-80 per cent.

The greater the wind speed, the faster people lose body heat and they feel colder.

The high-level of moisture amid windy conditions might lead to hazy morning over the weekend. The high-speed wind lifts the moisture to the upper layer of the atmosphere, creating a cloud like layer. As a result, the skies look hazy.

The weather could turn warmer from Monday. Sen claimed that he was not expecting any new western disturbance to affect the region in the next week.

Western disturbances are low-pressure areas or extra-tropical storms originating from the Mediterranean Sea, Red Sea and the Caspian Sea, which cause winter rainfall in the northwestern parts of the Indian subcontinent.

With regard to the departure of the shivery weather, weathermen claimed that it was not expected at least before the second week of February. In broader terms, if the actual minimum temperature remains four to five notches above normal for five to six consecutive days at this time of the year (after the third week of January), then it is considered the winter has departed.