Monsoon currents of moderate intensity are likely to enter eastern Sindh from the night of August 4, it said in a statement.
Under the influence of this weather system, it said, rain and thunderstorms with moderate and heavy falls were expected in Tharparkar, Umerkot, Mirpurkhas, Badin, Tando Muhammad Khan, Tando Allayar, Hyderabad, Matiari, Thatta, Sujawal, Sanghar, Shaheed Benazirabad, Khairpur, Sukkur, Larkana, Ghotki, Kashmore, Shikarpur, Jacobabad, Dadu, Jamshoro and Kambar Shahdadkot districts during August 5 and August 9.
Meanwhile, rains in Karachi were predicted from August 6 to August 9.
During this period, the temperature in the metropolis will stay between 26 and 32 degrees Celsius while humidity will stay under 80 per cent.
Westerly and southwesterly winds were also expected to blow in the city.
In the fresh forecast issued today, the Met office also cautioned that heavy falls may generate water-logging in low-lying areas of Karachi, Badin, Thatta, Sujawal, Tando Muhammad khan, Tando Allayar, Dadu, Jamshoro and Kambar Shahdadkot districts.
It further instructed the authorities to take all necessary precautions in case of an emergency.
Monsoon rains, that began in June, have wreaked havoc across the country killing hundreds of people. On her visit to Karachi on Monday, Minister for Climate Change Sherry Rehman said that Karachi recorded a historic over 600mm of rainfall [in July] and will see more in August.
Talking to reporters, she highlighted that building resilience in Karachi should be the prime focus of the government as the city had witnessed the worst of disasters during the three monsoon spells.