June and July are the peaking months for these two pockets in terms of Monsoon rain, while August and September observe a decline. For instance, Kochi receives 403 mm of rain in August while in September it reduces to 280 mm. Similarly August rainfall for Mangalore is a whopping 787 mm and 292 mm for September.
Goa also observes 592 mm of rain in August. The number falls to just about half 256 mm in September. Mumbai record 530 mm in August, while in September the rainfall figure drops to 312 mm.
The number of rainy days also reduces sharply. Kochi observes 14 raniy days (2.5 mm of rain or above) in September as opposed to 20 during August. Goa observes 13 and Mumbai 14 against 24 and 21 in August respectively.
During September the Southwest Monsoon begins retreating and the withdrawal commences from West Rajasthan, from first week of September. Retreating of Monsoon from most parts of Western Ghats takes place in October and coincides with the onset of Northeast Monsoon. This is why good rain is observed at some coastal stations during October.
During September there is a marginal increase (about 1-2 degrees) in the day temperatures due to decrease in rain and absence of cloud cover. They however, remain close to a comfortable level of 30°C. There is not much change in the minimums which record close to 24°C.
Picture courtesy: team-bhp.com