The casualty figures from Saturday's storms rose after 185 more bodies were counted in the city morgue, said Sardar Ahmed, minister of health for Sindh province, of which Karachi is the capital.
The initial number of dead had been reported as 43.
The country's economic hub, a dynamic but chaotic city with fragile infrastructure, frequently seethes with tension and street protests, some sparked by massive power outages. The atmosphere has been particularly tense since May 12, when political unrest left more than 40 people dead.
An official at the Edhi Foundation, which runs the morgue, said many of the victims came from Gadab Town, a cluster of villages with mud houses and other flimsy structures on Karachi's eastern outskirts.
Relatives have identified and claimed all 228 bodies, said Anwar Kazmi, a senior Edhi Foundation official. Among the 185 dead were eight children and 15 women while the rest were men, he said.
Most of the deaths were caused by collapsing homes but snapped power lines electrocuted many people in separate incidents, Ahmed said. At least 20 people were reported killed in electrocution incidents on Saturday.
"Forty-three bodies were counted in city hospitals last night and now 185 bodies have been identified in the Edhi Foundation morgue," he said.
A 22-year-old woman, her son, 2, and daughter, 3, were among the dead in Gadab Town, Karachi Mayor Mustafa Kamal said earlier.
Some 200 people were injured in the storm, he said.
Electricity was still disrupted in some neighborhoods Sunday. Residents, angry at having to spend a night without power to run fans or air conditioners in the sweltering summer heat, staged street protests, Kamal said.
Work on restoring the electricity supply had started and municipal workers were clearing storm-toppled trees, billboards and other debris from streets in the city on the Arabian Sea coast, he said.
A relief camp was set up in Gadab Town to provide food, medicine and shelter to people whose homes were destroyed or damaged there, said Murtaza Baluch, mayor of the neighborhood of mainly farm and factory workers.
Dozens of people died in rain-related incidents in Karachi last year and choked drains left many streets flooded with rain water that also disrupted traffic, power and communication lines.
But Kamal said authorities had cleared old drains and built new ones, preventing massive flooding this year.