Lonavala, Mahabaleshwar, Tamhini, Bhira, and several locations nestled in the Sahyadri ranges and the Western Ghats of Maharashtra experienced historically high rainfall ranging over 600mm in three 24-hour periods between July 6 and 8. This resulted in landslides, mudslides, and flooding, affecting road, rail, and air traffic.Parts of Lonavala — an important economic and strategic link between Mumbai and Pune in western Maharashtra — were temporarily paralysed. Many of these places are surrounded by dense forests and are tourist attraction spots. These locations are also important for the region’s water reserves, especially as catchment areas for the Krishna and Bhima river basins — these have over two dozen dams supplying water to downstream regions of western Maharashtra.So, what triggered such intense rain? We explain.The India Meteorological Department (IMD) classifies rainfall between 204 mm and 244.5 mm as “extremely heavy”, and any rainfall above 244.5 mm is “exceptionally high” and is near about the highest recorded rainfall at or near the station. Both are 24-hour values.During July 6-8, some locations in Maharashtra along the Western Ghats recorded exceptionally high rain. Lonavala, Bhira, and Mahabaleshwar were some of the wettest places receiving historic spells, shattering all previously known rain records. During these 48 hours, the surplus rainfall ranged from ~60 to 160%: Lonavala (1290 mm, +161%), Bhira (1121 mm, +73%), Tamhini (1110 mm, +125%), Shirgaon (960 mm, +58%), and Mahabaleshwar (916mm, +100%). Rainfall (in mm) during July 6-8, 2026. Source: IMDSuch washout rainfall spells were triggered by multiple favourable weather conditions pushing the monsoon into active phase, the IMD said. Last week, a depression had formed over central India, and it subsequently moved along Odisha and Chhattisgarh, attracting moist winds from the Bay of Bengal.In addition, the position of the monsoonal trough — an extending belt of low pressure area predominant during the monsoon — and the presence of another trough running parallel to the west coast together contributed to such intense rainfall along western Maharashtra.Geography-linked regional rainfallThe geographical location and orography — height, form, and spatial distribution of mountainous regions and elevated terrain — have big roles to play in the region’s weather, particularly on the rainfall during the southwest monsoon season.Story continues below this adWhenever there are active and favourable weather conditions in the Arabian Sea, there is a heightened rainfall over the ghat areas of Pune, Raigad, Satara, and the pockets nestled inside the Sahyadri ranges. These locations, specially characterised for receiving an annual rainfall of more than 100 cm, are confined to the coastal belt yet adjoining the Western Ghats — that is, the districts of Thane, Raigad, Ratnagiri, and Sindhudurg, and the western hilly parts of Pune, Satara, and Kolhapur.Also read | Mumbai faces 48 more hours of torrential rain as floods, landslides cripple MaharashtraGeographically, the windward side (sea-facing and to be hit by moist winds) receives higher rainfall amounts than the leeward side, often nicknamed as the rain-shadow belt. The difference of rainfall characteristics in July between the western and eastern parts of districts in central Maharashtra adjoining the Western Ghats is mainly owing to the influence of orography on rainfall extending up to a certain distance on the leeward side, according to a 1981 report by IMD, Pune titled “A theoretical study regarding heterogeneity of rainfall over Madhya Maharashtra”.Maharashtra is among the select Indian states where there is a significantly increasing rainfall trend. Heavy rainfall event days, too, are increasing over Konkan, with Palghar district showing an increasing rainfall trend both during the monsoon season and annually. Maharashtra has records of the frequency of heavy rainfall events lasting more than 20 days during the southwest monsoon season, as stated in the “Observed Monsoon Rainfall Variability and Changes during Recent 30 years (1989-2018)”.Historic recordsMost of these locations are not new to such extremely heavy rain spells, particularly during July and August, which are among the highest rainfall receiving months for Maharashtra. Story continues below this adRainfall records maintained by IMD (1941-1990) stated that Lonavala’s highest single-day was 578 mm recorded on July 23, 1990. For the same period, Mahabaleshwar’s wettest day was on July 20, 1896, when the hill station clocked 458mm; for Bhira in Raigad district, it was 713 mm on July 24, 1989.NewsletterFollow our daily newsletter so you never miss anything important. On Wednesday, we answer readers' questions.SubscribeSince there are no regular Met observations taken at Tamhini, the known wettest spell (24 hours) gathered from other sources is said to be 695 mm and the wettest 3-day period was 1055 mm (1975-2013). Researchers at the Indian Institute of Tropical Meteorology performed rainfall analysis for this period over Tamhini and found that despite the location lying on the leeward side of the Western Ghats, the rainfall there is more than that of many stations lying on the windward side of these ghats. The study concluded that Tamhini’s rainfall ranks at the top in the north peninsular region and 5th overall in India.Interestingly, Tamhini’s mean rainfall for July is 2658 mm, which is close to that of Cherrapunji (2876 mm), considered among the world’s wettest places. In fact, there are more such locations in this stretch of the Western Ghats with high mean July rainfall: Shirgaon (1953 mm), Ambavane (2113 mm), and Davdi (2219 mm).