Thailand's recent "rain bombs" have triggered concern about a repeat of the massive floods in 2011 that caused widespread losses, paralysed cities and stung the economy.
On May 25-27, Thailand experienced a repeat of this weather phenomenon, characterised by torrential downpours that cause instant damage.
Last month's rain bombs were caused by a stronger southwest monsoon sweeping across the Andaman Sea and the Gulf of Thailand, compounded by a strong monsoon crossing upper Thailand and the upper southern region.
The rain bombs followed a series of unusual climate patterns that have occurred in the country since the start of this year.
May is considered an early start to the rainy season. Thailand's summer in April was beset by lower-than-average temperatures, which followed the 7.4-magnitude earthquake in late March with the epicentre near Mandalay, Myanmar.
Statistics from May 1-14 indicated that Bangkok accumulated rainfall of 188.5 millimetres, a 95% increase compared to the average 30-year rainfall of the Drainage and Sewerage Department of 96.7mm.
Assoc Prof Seree Supratid, director of the Center for Climate Change and Disasters at Rangsit University, said that La Niña, a pattern of cold ocean temperatures in the central and eastern tropical Pacific, has altered its pattern, driving cooling temperatures across the country in April.
"There is climate instability and unpredictable seasonal shifts. Rain bombs have emerged as another unpredictable weather pattern presenting challenges of intense rainfall over a short period that is difficult to predict," he said.
The average rainfall for May was about 214mm, which is higher than the average over the past 30 years, he said.
However, it is too soon to predict massive flooding for this year.
Assoc Prof Seree said downpours from June to July are expected to ease, and dry weather will return from August to September. Heavy rainfall should make a comeback in October.
The level of water in reservoirs nationwide now stands at about 42 billion cubic metres, or 56% of total capacity, he said, leaving ample room to store more water from rainfall.
"This is unlike the massive floods in 2011 when Thailand had accumulated annual rainfall of over 1,400mm and the water level in reservoirs was higher than 60%."
The academic said Bangkok has done well in managing the risks of flooding. AI systems are used in water management, projecting the volume and direction of the water three hours in advance, making water drainage much faster. And as some 1,900 canals are now being dredged, more water can flow through.
Some risk-prone areas in the capital have installed additional water pumping systems to help increase drainage.
In other provinces, water has been released from 21 large reservoirs to cope with the rainfall. This is done under constant assessment to adjust the drainage plan to developing situations.
The Royal Irrigation Department's water pumping stations have been improved so that water from the North no longer has to pass through Bangkok, said Assoc Prof Seree.
Instead, the water flows east to the Bang Pakong River, while to the west, water is diverted to the Tha Chin River through the Krathum Baen station, which has an efficiency rate of 45 cubic metres per second.
Assoc Prof Seree added: "Without advanced tracking sensor technology, many provinces remain at risk.
"At present, our forecasting capacity only allows for an advance warning of 3-5 days for the public to prevent losses and keep themselves safe. Residents need to rely on a strong community to monitor the weather changes."
Seree: 'Many provinces at risk'