When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Mumbai is roughly less than Golden Triangle Rgnl. You can assume this to be the case over the next 0 days.
You can imagine temperatures to be in the 34 °C range in May. The weather in Golden Triangle Rgnl is generally colder than Mumbai's. As flight availability is subject to become more limited as peak season approaches it is ideal to book in a timely manner.