Hilly states of North India will simultaneously come under the influence of western disturbance, resulting rain and thundershowers. Thunderstorm accompanied with lightening and hailstorm at few places and squally winds are likely on 20th and 21st May.
This system along with an induced Circulation over the plains will result in some Pre Monsoon rain and thunderstorm activity over Punjab, Haryana, Rajasthan, Delhi, West Uttar Pradesh, West Madhya Pradesh, North Gujarat, Madhya Maharashtra, and Marathwada today. Parts of North India will see some dusty winds as well.
Wind pattern will change from dry and extremely hot northwesterly to light and moist easterly. The day temperatures are expected to dip by 2-3°C, albeit with a spike in the sweat and sultry conditions. Heat wave may abate for couple of days but build up again after mid week.
Rain and thunderstorm activities main commence over Western Himalayas from April 13th. Isolated pre-monsoon activities such as thunderstorm, dust storm and light thunder showers may occur over parts of Punjab, Haryana, Delhi and West Uttar Pradesh between April 13 and 17.
Intensity and frequency of Western disturbances are reducing and there is no weather system developing over northern plains. Moisture feed is also unavailable from Bay of Bengal or Arabian Sea. Therefore, conditions are not becoming favourable for commencement of any pre monsoon activity over North India until first 10 days of April.