Heavy rain with thunderstorms lashed Delhi on Monday afternoon with the freak weather catching people by surprise. Traffic was disrupted throwing life out of gear. The weather office has forecast four days of rain with the maximum temperature plunging by 10 degrees Centigrade.

The main reason for the unseasonal rain is the “Western Disturbance”, Dr Naresh Kumar, Senior Scientist at IMD. The western cyclonic disturbances are low-pressure systems that originate over the Mediterranean Sea. Under the influence of subtropical westerly jet streams, these wind systems reach India and cause rainfall.

A warning of heavy rainfall has been issued for the Western Himalayan region which is expected to receive more than 6.5 cm of rainfall.

Delhiites took to Twitter to express surprise over the unexpected weather with some saying that they could not recall having ever seen such rain in May over the last two decades.

India Meteorological Department today said almost all states across the country are expected to see rain for the next four days. It has been raining in most parts of the country for the past two days, it said.

“There’s a possibility of hailstorms in Punjab, Haryana, and the western Himalayan region as wind is coming from the West and also from the Bay of Bengal,” Dr Kumar said.

East India is also cloudy and there are chances of rain for three to four days, the weather office said, adding that there could be heavy rainfall in the North East for three days as well.

Heavy rain is also expected in the southern states including Tamil Nadu, Kerala, Andhra Pradesh and Karnataka.