The monsoon, incidentally, is not the rain per se
Rather, it's the wind that blows the rain in across the Arabian Sea or Bay of Bengal (depending). It finally hit today, and I have all the windows open for the first time in months (before the monsoon, leaving the windows open invites mosquitos, which means dengue).
The first thunderstorm is forecast for next week; I'm really looking forward to it (Mumbai has had zero precipitation since August). Last year's monsoon was late and disrupted, but all the old guys playing cards out on the corner are very sure it will be early and strong this year; the fishing fleets have also moved their boats in from the roads to the back bay and are starting to take down their fish drying racks. Between old guys' knees and fishermen who still use lateen sails, I'm willing to concede there's a lot of good intuitive meteorology there.
It's interesting. A US meteorologist came here to give a lecture series and everyone kept asking him what the monsoon is like in the US, and he made very little progress explaining that we don't have one, and that it can rain pretty much any time of the year (and that's in fact mostly what meteorologists worry about in the US). Indian meteorologists, by contrast, need to be able to predict as accurately as possible, as soon as possible, the one particular day that the rains start. Lives depend on it. (The full monsoon rain is different from the thunderstorms that precede it; we won't have the full monsoon until mid-June probably, but it then won't stop raining except for a few hours at a time until mid-August.)
The city caught a lot of hell for being unprepared last year for the flooding that happened. Oddly enough this wasn't the "fault" of the monsoon but of the fact that last year there were several "daily rains" (ie, what Americans just think of as "rain"
during the spring, which clogged up the storm drains with debris before the city had time to clear them. This is a new development in the past decade or so, and a disturbing indication that the monsoon system is being disrupted by climate change. About two billion people depend on that system for their caloric intake, ultimately, and two of the nations they live in have the bomb. 
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in which moisture streams up from the Pacific during the summer months and can create showers.
And here in California, it seldom rains from May through mid-October, although we are apparently going to get doused tomorrow, just in time for my flight to NYC. 
