Unlike some parts of Java where it is still raining, a large section of Sumatra is approaching the dry season.
If earlier hot spots were only widespread in Riau, they have now appeared in a number of other provinces.
"The number of hot spots has increased by more than 100 per cent because only 12 were detected in four regencies a day earlier," said the Meteorology, Climatology and Geophysics Agency (BMKG) Pekanbaru station data analysis staffer, Yudhistira Mawaddah, on Monday.
Based on satellite images gathered by BMKG Pekanbaru on Monday morning, 67 hot spots were detected in Sumatra. Riau still dominates with 26 hot spots, followed by North Sumatra with 20 hot spots.
Hot spots in Aceh and West Sumatra, provinces that were earlier free of hot spots, have appeared in eight and seven places respectively. Another province in which hot spots have been detected is South Sumatra with six hot spots.
"Yesterday, there were only 15 hot spots in Sumatra. The increase in the number of hot spots is due to the minimal rainfall," said Yudhistira.
For Riau, hot spots have spread from seven to 12 regencies and cities. Based on the latest observation, Rokan Hilir regency is recorded to have the most number, with seven hot spots.
Hot spots have also appeared in Bengkalis (5), Dumai (5), Pelalawan (5), Siak (2), Indragiri Hulu (1) and Meranti Islands (1).
"Many of the 13 hotspots in Riau have been confirmed as fires, with a likelihood of over 70 per cent. Fires have also been confirmed in Rokan Hilir, Dumai, Bengkalis, Pelalawan, Indragiri Hulu and Meranti Islands," he added.
Despite the presence of additional hot spots, regions hit by land and forest fires have so far not yet been affected by haze. According to Yudhistira, visibility recorded by four observation posts was still between 5 and 7 kilometers, or still categorized as normal.
"Air quality earlier touched 124 PSI, categorized as unhealthy, on Sunday evening, but today it has improved and dropped to 53 PSI, or a medium level," he added.
"Haze covering Pekanbaru originated from land and forest fires in Dumai, Bengkalis and Rokan Hilir, as the wind direction is currently blowing from the northeast to the south. Moreover, Pekanbaru is currently free of land and forest fires," said Yudhistira.
He did not dismiss the notion that the haze covering parts of Jambi province most likely came from land and forest fires in Pelalawan and Indragiri Hulu.
"Wind blowing at a speed of up to 29 km/hour might have carried haze from forest fires in Riau to neighbouring provinces," he said.
The BMKG Pekanbaru station has warned every party to remain alert as the temperature, ranging from 31.5 to 33.5 degrees Celsius, would potentially trigger land and forest fires.
"The weather in Riau is generally cloudy, and light intensity rain will fall sporadically in the afternoon and evening. Regions where rain is likely to occur are in the western and southern parts of Riau, such as Kampar, Kuantan Sengingi and Rokan Hulu," he said.
Separately, Riau Environmental Office head Yulwiriawati Moesa said the Riau provincial administration was currently making technical preparations to ask the central government to assist in weather modification technology to make artificial rain.
The Riau governor will also propose that the central government provide firefighting helicopters and aircraft at the haze emergency command post at the Roesmin Nurjadin Airbase in Pekanbaru.