India recorded one of its driest Junes in 146 years as the southwest monsoon stalled despite arriving on time. The rains have since revived in some regions, but the science of the stall reveals why much of the country stayed dry.

The monsoon should have reached Delhi on June 27, but the capital is still waiting as dry desert winds and a developing El Nino stall the rain across north India. Here is the science behind the delay and when the showers are finally expected to arrive.