Shimla, July 19 -- The India Meteorological Department (IMD) has issued a red alert for heavy rainfall in parts of Himachal Pradesh on July 20 and 21, warning of flash floods, landslides, rising river levels and widespread disruption as monsoon activity is expected to intensify across the state from the night of July 18.

Speaking to the media in Shimla on Saturday, senior scientist at the IMD's Meteorological Centre, Shimla, Sandeep Kumar Sharma, said the weather system is expected to remain active until at least July 24, with the most intense spell likely on July 20 and 21.

"The weather is expected to become active from the night of July 18. Light to moderate rainfall will occur across many parts of the state, while heavy to extremely ...