11-08-2025
As per 123-year rainfall data, many locations in State vulnerable to disasters in August
This week marks the seventh anniversary of the mega flood that claimed close to 500 lives in the State. Although rainfall this August has been subdued so far, a cursory glance through the 123-year rain data of the Indian Meteorology Department (IMD) in Kerala reveals that many spots in Kerala are vulnerable to disasters in August, given the rainfall pattern in terrains across the State.
A map drawn by P.S. Biju, senior scientist with the IMD, Thiruvananthapuram, using machine learning and GIS techniques and rainfall data collected from 110 weather stations in Kerala for the period between 1901 and 2023, shows that many locations in the State, especially parts of north Kerala, Idukki and Pathanamthitta, are vulnerable to disasters in August given the distribution of heavy rainfall.
What the colours indicate
In the map annexed with the story, the spots marked 'red' witnessed a minimum of three heavy rainfall events in August, and two intense rainfall events were recorded in areas marked in orange. The areas marked in yellow witnessed at least one such heavy rainfall event, while green denotes that for many years those areas have not witnessed any such events in August, said Mr. Biju.
Though August has emerged as a dreadful month for Keralites who witnessed the 2018 and 2019 floods, the month receives relatively less rainfall compared to June and July, the two wettest southwest monsoon months in Kerala. In 2018, Kerala had received good pre-monsoon showers in May. This was followed by above-normal rainfall of 751.5 mm in June and excess precipitation of 857.8 mm in July. By this time, the cumulative excess precipitation in three months had saturated the soil and waterbodies.
This was followed by the record precipitation of 820.9 mm of rainfall in August, against the monthly average of 445 mm, mainly in the third week of the month, submerging a vast tract of the areas in south and central Kerala. In 2019 as well, August had witnessed a record precipitation of 950.5 mm of rain, flooding southern Kerala. However, the severity of the flood was relatively less in 2019 compared to 2018, as the rainfall was deficient in the preceding months, especially in June (359 mm), and normal in July (574.3 mm).
The flood of 1924
During the 'great flood of 1924' in Kerala, also known as the 'great flood of 99' and another major flood in 1961, the calamity occurred in July, unlike August in 2018 and 2019. It was only five times in the recorded history of Kerala that rainfall crossed 800 mm in August, and two times were in this millennium. This year, the IMD has forecast below-normal rainfall for August in 2025, and the rain has been subdued over most parts of the first half, except for a couple of short-lived intense spells.
