Patna, March 26: Residents can expect some respite from the dry and hot weather as the Met office has predicted overcast conditions and showers across the state for three days from Monday.

Weathermen have attributed the rainy conditions to the Nor'wester, the phenomenon that brings sudden showers in summer.

While southern areas of Bihar are expected to get light showers and residents in the central part have to console themselves with clouds, the Met office has issued an alert for hailstorm in north Bihar.

Met centre director Ashish Sen said the Nor'wester was the outcome of the confluence of a western disturbance coming from north India and a current cyclonic circulation over the Gangetic Bengal.

"The confluence of the two systems is expected to lead toNor'wester activities in Bihar and the neighbouring regions," said Sen. "The entire north Bihar may experience sudden thunderstorms on Monday and Tuesday. Besides, there is a possibility of hailstorm at a few places as well. Places in south Bihar would get light rain and the central parts are expected to remain cloudy on Monday."

Rainfall in the months of March and April are commonly referred to as "mango rains" in Bhagalpur and Muzaffarpur districts, as the showers are considered crucial for the growth of mangoes, litchis and summer crops cultivated in abundance there.

The rain will also bring down the temperature by a few notches during peak Nor'wester activities that usually lasts not more than two hours. The average wind speed in Patna during the expected Nor'wester on Monday is likely to be around 28kmph against Saturday's 9kmph.

Meteorologists said the wind speed would be comparatively higher if the thunderstorms form in the afternoon or evening. "The wind speed would be comparatively higher in places facing hailstorm," said a senior meteorologist. "On an average, the wind speed during peak Nor'wester activities is expected to be around 40-60kmph."

While the barometer keeps jumping, doctors advised residents caution against the fluctuating weather.

"Residents should not go outdoors on an empty stomach and must increase intake of fruit juices," said physician Diwakar Tejaswi. "Children should be given vaccination for flu and diarrhoea. The people are advised to wear light clothes."

The Nor'westers hitting Bihar normally originate from the Chotanagpur plateau region when the air heats up and gains altitude with moisture support from an anti-cyclonic circulation or similar weather system in the China Sea or Bay of Bengal.

Nor'westers started quite early in Bihar this year, as one hit the state around March 10. The one expected in the coming week would be the third this month. These frequent Nor'westers have been attributed to a higher sea surface temperature in the Pacific Ocean, also known as the El Niño phenomenon.

The temperatures have also been rising up since the beginning of March with maximum temperatures remaining at least a couple of notches above normal on most days.

On Saturday, the maximum temperature in Patna was recorded at 37.4°C and weathermen said the mercury column would only travel north after the Nor'wester and overcast conditions pass the state.