Rainfall data usually available with IMD and for this Director IMD can be contacted. Civil Aviation department also collect such data and Air Port Authority may provide useful information.
Thank you Mr. Anand Gupta. I want rainfall data of last 30 or more years. So if you can tell me the exact procedure and concerned person for getting this data,I will be very thankful to you.
Depending on your specific purpose for obtaining the data and the time step, you may check GHCN. It is global monthly rain gauge data which is downloadable for free at http://www.ncdc.noaa.gov/ghcnm/
There are also several global rainfall products that are grid-based on gauge data only like CRU or mixed with satellite/radar/reanalysis data. Look at this guide for all climate data and filter it for rainfall: