His arrival came as thousands of people fled a major city in central Pakistan as rivers nearby swelled.
The UN, relying on Pakistani figures, says the number of people affected by flooding over the past two weeks is 13.8 million — more than the combined total of the 2004 Indian Ocean tsunami, the 2005 Kashmir earthquake and the 2010 Haiti earthquake, although the death toll in each of those disasters was much higher than the 1,500 people killed in the floods.
The widespread crisis has overwhelmed the government and frustrated citizens who have complained about slow or non-existent aid efforts. A person is considered "affected" by the floods if he or she will need some form of assistance to recover, either short-term humanitarian aid or longer-term reconstruction help, the UN said.
Amid the relentless rains, Zardari — an unpopular figure to begin with — took off for a visit to France and Britain.
His aides said he had to undertake the trip for diplomatic reasons, especially in the UK, whose Prime Minister David Cameron had recently accused Pakistan of exporting terror.
But the timing of trip struck a raw nerve among many who said Zardari should have stayed with his suffering people — even though the president, fearful of assassination, rarely makes public appearances in Pakistan anyway. The criticism was particularly harsh after reports that he'd visited his family's elegant chateau in France.
Zardari returned first to the southern city of Karachi and was expected back in the capital, Islamabad, on Wednesday.
He is set to meet with the chief ministers of the provinces to map out a rehabilitation program, said Fauzia Wahab, spokeswoman for the ruling Pakistan People's Party.
In Punjab province, the normally bustling city of Muzaffargarh looked largely deserted Tuesday after large numbers of people left following flood warnings the previous evening. Many men, however, stayed behind to guard homes and businesses.
"There is no doubt that our city is almost empty now," said Mohammed Saleem, 42, a shop owner who sent his wife and children to Multan city.
The local government hospital had staffing shortages because many doctors and other workers had decided to leave.
"We have put sandbags around our hospital to protect it from any possible floodwaters, but we do not know whether it will help," said Ashiq Malik, a hospital official.
The population of Muzaffargarh is around 250,000, said Hassan Iqbal, a senior government official in Dera Ghazi Khan district. The evacuation warning was issued only after authorities assessed that the floods could hit the city, Iqbal said.
"It may not happen, but there is a danger to the city," he told The Associated Press.
Pakistani Prime Minister Yousuf Raza Gilani has called the crisis the worst natural disaster in Pakistan's history and appealed for international help. The US and other countries have already donated millions worth of aid, and the American military has dispatched six helicopters from Afghanistan to assist in aid delivery and evacuations.
The hardest hit region has been the northwest, which also is the epicenter of Pakistan's fight against Al-Qaeda and the Taleban. But as swollen rivers have flown south and east, Sindh and Punjab provinces have also been affected.
Rescue work has been hampered by ongoing monsoon rains, which have washed away roads and bridges and made it impossible for helicopters to fly at certain times.
The floods hit the country at a time when the government is already struggling with a faltering economy and a brutal war against Taleban militants that has killed thousands of people. The patchy government response has given room for Islamist groups, some allegedly linked to militant outfits, to step in and offer their own aid to displaced and hungry flood victims.
