Scores of people suffering from dehydration and sunstroke were being treated at hospitals across the worst-hit southern Indian state of Andhra Pradesh, said D.C. Roshaiah, the chief relief official in the state.
At least 81 more deaths were reported throughout Andhra Pradesh during the last 24 hours, taking the toll to 637.
At least 119 deaths have been reported in Nalgonda district and 85 in East Godavari district, where the temperature hit 117.50 F last week. Another 98 people died in neighboring Prakasham district, Roshaiah said.
Andhra Pradesh is battling its worst drought in 40 years due to lack of rain last year.
Last year, a heat wave killed more than 1,000 people in the state, most of them elderly and unable to bear temperatures that reached up to 122 degrees. Tin-roofed shanties were like ovens for hundreds of thousands of poor people.
Dry hot winds have lashed the three coastal districts Friday, and night temperatures were not expected to change much, Roshaiah said.
"We have asked administration officials in all the districts to set up drinking water kiosks and make oral rehydration salt sachets available in villages in the heat wave hit areas," he said.
The weather office in Hyderabad, the state capital, warned Friday that heat wave conditions will continue for at least another 48 hours, Roshaiah said.
The heat has also taken a toll on the state's poultry and agricultural industries. Andhra Pradesh is the main supplier of eggs to other parts of the country.