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 heavy rainfall is likely in several districts over the next few days," Sharma said. He said a yellow alert has been issued for Chamba, Kangra, Kullu and Mandi for July 18, where isolated places are likely to receive heavy rainfall. The weather activity is expected to intensify on July 19, with the IMD issuing an orange alert for Kangra, Mandi and Shimla for heavy to very heavy rainfall. Yellow alerts have also been issued for Chamba, Hamirpur, Kullu, Sirmaur, Solan, Una and Bilaspur. Sharma said the most severe weather conditions are expected on July 20, when a red alert has been issued for Chamba, Kangra, Mandi and Sirmaur, where isolated places may experience extremely heavy rainfall. An orange alert has been issued for Una, Bilaspur, Hamirpur, Kullu and Shimla. The revenue, horticulture and tribal development minister, Jagat Singh Negi on Saturday said the Himachal government has made comprehensive preparations to deal with any emergency arising out of the IMD's forecast of heavy rainfall over the next four days, with disaster response teams strategically deployed and all departments placed on alert. Negi said NDRF teams have been deployed at identified vulnerable locations, including Shimla, Jauri, Bhurpur and near Pandoh in Mandi district, to ensure a quick response during emergencies....