Principles are Used to Predict the Occurrence of Rainfall In India

• After the sun has entered Mrigshira nakshatra towards the end of May the south-west monsoon begins to strike Kerala coast. When sun enters Ardra (22-23rd June) every year monsoon advance towards northern India.

• When sun reaches and crosses six degrees in Gemini, the monsoon arrives in North India (around June 22) and when sun reaches ten degrees in Virgo on September 26 the monsoon begins to withdraw in North India.

• When the sun enters Hasta nakshatra, it causes rain in Bihar, which is known to an average Bihar farmer as Hathiya rain. But by that time monsoon withdraws from the rest of northern India.

• When the sun enters Chitra, it continues to cause rain in Bihar particularly in north-east India.

• When the sun enters Swati. It causes some occasional rain otherwise the south-west monsoon withdraws totally, in Indian tradition there is reference to the bird called chatak which supposedly waits for the rain-drop of swati.

• The moon, in certain positions, ‘nakshatras’ (constellations/star) joining, with other planets or when inspected by them can cause or hinder rain.

. • There will be rain when Mercury transits Cancer and join Venus in the north India after August 3.

• The presence of Jupiter and Venus together in Rohini star shows torrential and untimely down pour of rains.

• Mars and Rahu together inspected by Saturn causes lightening and cloud bursts.

• Cyclones on the Andhra Pradesh coast are likely to occur close to periods of sunspot maxima when the planets Jupiter, Saturn, Rahu (Ketu) and Uranus form even loose aspects of Kendra (square) and Samagama (conjunction) between themselves. These indications are strengthened whenever either Virgo or the 12th from it are afflicted.

(i) Rain gauging – According to Varahamihira, rainfall should be collected in a vessel whose capacity is an adhaka. An adhaka has been defined as the quantity of rainfall, which falls to the
brim of a vessel 20 inches in diameter and eight inches deep. Four such adhakas constitute a drona. If conception of clouds is due to all the five conditions of wind, rain, lighting, thunder and clouds, says Varahamihira, then the quantity of subsequent rainfall will be one drona and this will fall over an area of 400 square miles. If the conception of clouds has been due to wind alone, the resultant rainfall will be three adhakas. If due to lightning, the rain will be nine adhakas. If due to thunder and other factors affecting rainfall, twelve adhakas.

• If there is rain on the day on which the Moon asterism is either Hastha or Poorvasshadha or Mirgasira or Chittra or Revathi or Dhanistha, then on the corresponding days of the next lunar month, there will be 16 dronas of rainfall.

• If there is rain on the day on which the Moon asterism is either Sravana or Makha or Anuradha or Bharani or Moola, then on the corresponding days of the next lunar month, there will be 14 dronas of rainfall.

• If the Moon resides in either Satbhistha or Jyestha or Swathi, there would be 4 dronas of rainfall on the corresponding days of the rainy seasons. If in Krittika, 10 dronas; If in Poorvaphalguni, 25 dronas; If in Vishakha or Uttarashadha, 20 dronas; If in Ayslesha, 13 dronas; If in Uttarabhadrapada or Uttaraphalguni or Rohini, 25 dronas; If in Aswini, 13 dronas; If in Aridra, 18 dronas.

• If the moon in above asterism suffer from malefic influence either aspect or conjunction, there will be neither rain nor prosperity in the land. If the benefic planets pass through above asterism or the moon in above asterism should remain unaffected by malefic, rainfall would be good.

(ii) Hour of rainfall – The very hour of the occurrence of rainfall can also be determined; for, says Varahamihira, clouds ‘conceiving’ during the day will be delivered at night and clouds ‘conceiving’ at night will be delivered during the day; clouds ‘conceiving’ in the twilight of the evening deliver during the morning twilight, and vice-versa. Again, if at the time of conception, clouds have appeared in the east, then at the time of birth, they will appear in the west; and so on with the other quarters. Similarly, if at the time of conception the wind has blown from the east, then at the time of rain, it will blow the opposite quarter.

(iii) Rain in the immediate future – While ancient meteorology can predict rain long in advance, is it no difficult thing to forecast rain in the immediate future. During the rainy season, immediate rainfall is indicated: If the sun at the time of rising is exceptionally bright and red, or If the taste of water is insipid, or the color of the sky or sunset rainbow is seen in the sky, or If salt begins to sweat, or If fish in tanks jump from water on the bank, or If metal vessels emit a fishy smell, or If ants, with their eggs, move from one place to another.

(iv) Forecasting rainfall, floods and weather vagaries – Of the several methods recommended by classical writers for forecasting rainfall, floods and weather Vagaries, the most important ones are:

(a) the lunar new year chart,

(b) time of pregnancy of clouds,

(d) Sun’s entry into Capricorn,

(e) Rohini, Swati, and Ashadha Yogas, and

(f) mutual dispositions of planets at a given time.