Key Highlights (1950–1975)

• Earliest Arrivals: The earliest monsoon arrivals for this entire 25-year window happened on May 29, recorded in three specific years: 1956, 1962, and 1971. [1]
• The Unique June 21, 1961 Onset: In 1961, the monsoon had a notably delayed arrival on June 21. This date is highly famous in Indian weather history because the monsoon hit both Delhi and Mumbai on the exact same day. 
• 1975 Onset: As the period closed out, the monsoon arrived in Mumbai on June 13, 1975. 
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Mumbai Record Rains July 2005. See Details here: 

26 July 2005 ..
>1 hour highest rainfall at Mumbai Scz : 190.3 mms (3.30 to 4.30 pm)
>3 hour highest rainfall at Mumbai Scz : 381 mms (2.30 pm to 5.30 pm)
>6 hour highest rainfall at Mumbai Scz : 648.4 mms (2.30 pm to 8.30 pm)

Rainfall in Mumbai:
August 2015: 
Colaba 188 mms...Lowest in last 10 years ....Driest ever August was in 1943 with 83.3 mms, 122 mms in 1972, 125 in 1968.
Wettest August for Colaba: 1265 mms in 1958.
2015 Season's Total  till August end: 1335 mms( -426 mms)....

Santa Cruz 154 mms....3rd Driest ever...Driest August was in 1972 with 108.6 mms, in 1966 it was 123 mms, 
Wettest August for Santa Cruz: 1254 mms in 1958.
2015 Season's Total till August end:1620 mms ( -286 mms).

July 2015:
For Mumbai SantaCruz, July 2015  was the 3rd driest July on record..This July (2015) saw 360 mms of rain, and the previous lowest was in the drought year 1971, when 385 mms was recorded, and all time lowest was in 2002 when only 103 mms was recorded in July..

June 2015:
Mumbai Santa Cruz sees the wettest June ever with 1106 mms. The previous record was 1037 mms in 1971.
However, Colaba measured 860 mms,far from its record June rainfall of 1280 mms in 1985.