Low Frequency (LF) radio telescope has been utilized to investigate the onset and stable conditions of Indian monsoon. Round-the-clock observations of atmospherics have been taken at 40 kHz over Kalyani (22.98°N, 88.46°E), West Bengal for six consecutive years 2011 to 2016. The average noise level of atmospherics taken round-the-clock at 40 kHz for 15 days before the onset as well as for the same period from the onset date of the monsoon have considered for all the individual years. We have also considered temperature, dew point, wind speed, humidity, sea level pressure and visibility for the same period of 15 days before and after the monsoon onset. Under the stable condition of the monsoon a characteristic variation has been noted in the atmospherics record. This paper reports a comparative study of precursory phenomenon in the atmospherics record during the onset of Southwest monsoon. Some related meteorological parameters besides Doppler Weather Radar information at such time have been taken into consideration at length. The recorded precursory phenomena have been examined and their probable explanation is given in terms of electrical discharges at such times.