Impact of prevailing atmospheric conditions on diurnal variability of the pre-monsoon rainfall over a tropical location, Kolkata

•Pre-monsoon rainfall over Kolkata is categorized on the basis of time of occurrence.•Rain events are categorized as expected (14:30 IST-18:30 IST) and delayed (after 18:30 IST).•Small value of the IWV to LWP ratio results in significant precipitation for the delayed events.•Ground level temperature of the delayed events exhibits 1 K higher values than the expected ones.•Variation of CAPE shows discernible increasing trend prior to two types of rain events.