Fires in South Sumatra, South Kalimantan and Central Kalimantan provinces show no signs of abating, despite stepped-up efforts to contain them.
The situation is made worse by tropical cyclone Phanfone hovering over the Philippine sea, and sucking in moisture over parts of Indonesia, an official said.
This means weather in the lower parts of Sumatra and Kalimantan will likely continue to get drier in the coming days, worsening fires and haze.
"We forecast slightly higher pressure on Saturday there, or cyclone Phanfone growing bigger," Mr Lutfi Fitriano, a weather forecaster at the national meteorological, climatological and geophysical bureau in Jakarta, told The Straits Times.
The forest and plantation fires in South Sumatra, South Kalimantan and Central Kalimantan have raged in recent days, affecting flight and shutting schools there.
The northern part of Kalimantan, Central Sumatra - which includes Riau province - and North Sumatra may, however, see some light rain in the coming days.
"Riau is wet enough, therefore it is safe from fire as they have ample rain," Mr Lutfi added. Riau is the second-closest province to Singapore, after Riau Islands province. Dumai city in Riau province was the epicentre of last June's haze when Singapore and Malaysia saw record-high PSI.
The total number of hot spots detected in Kalimantan was 389, and 31 in Sumatra yesterday, Singapore's National Environment Agency (NEA) said in an update on its website. But the low count in Sumatra was due to partial satellite coverage.
Central Kalimantan governor Teras Narang said the haze thickened yesterday. He will hold a coordination meeting today with all regency heads in his province to discuss ways to step up efforts to fight the raging fires.
"The haze has gotten very, very severe. Schools are closed, the number of residents with respiratory illness jumped, and flights have been affected," Mr Teras told reporters yesterday.
Water bombing operations in Central Kalimantan were partially impeded yesterday as the haze was too thick for the helicopter to operate, the provincial head of disaster mitigation agency, Mr Muchtar, told Kompas.com, the news portal owned by Indonesia's largest newspaper.
"We can barely see our neighbour's house 10 metres away," Mr Muhammad Muza, a Banjarbaru resident in South Kalimantan, told local news portal Harianterbit.com.
The number of people suffering from respiratory illness in the South Sumatran capital of Palembang almost doubled to 4,839 last month, from 2,852 the previous month. Visibility level in parts of the province fell below 500m.
Indonesia's disaster mitigation agency chief Syamsul Maarif has deployed 2,200 military officers and 1,050 policemen to take part in the ground firefighting efforts.
"Law enforcement must continue to be stepped up," Mr Syamsul said.