Heavy rain forecast for Sikkim as Teesta basin remains flood-prone; Mangan records 15.2 mm in 24 hours

The India Meteorological Department (IMD), through its Meteorological Centre in Gangtok, has issued a seven-day rain forecast warning of continued light to moderate rainfall across most parts of Sikkim, with heavy to very heavy showers expected at isolated places from August 1 to August 6, 2025. The weather bulletin highlights increased vulnerability in several districts, especially in areas along the Teesta River basin, already reeling under the effects of flooding and sedimentation from past disasters.

According to rainfall data recorded in the last 24 hours (ending August 1, 2025), Mangan district received the highest rainfall at 15.2 mm, followed by Soreng district at 3.0 mm and Damthang with 4.8 mm. Meanwhile, most other stations across Gyalshing, Pakyong, and Gangtok districts registered minimal to no rainfall, with places like Yuksom, Dentam, Khanitar, and Kabi recording 0.0 mm. Gangtok itself received only 1.4 mm, indicating varied rainfall distribution across the state.

The forecast bulletin, based on UTC observations and numerical weather prediction (NWP) model outputs, predicts light to moderate rain or thundershowers at most places in Sikkim for the next seven days, with localized heavy to very heavy rainfall particularly on August 2, 3, and 4. A red flag has been raised for areas in Mangan, Gyalshing, and Namchi where one or two locations may experience very heavy downpours, further raising flood concerns.

Weekly Rainfall Forecast Highlights

Day 1 (Aug 1 - Aug 2): Light to moderate rain likely across all districts; heavy rain possible at isolated places.

Day 2 (Aug 2 - Aug 3): Heavy to very heavy rainfall expected at one or two locations, especially in Mangan and Gyalshing.

Day 3 & 4 (Aug 3 - Aug 5): Continued rainfall with very heavy showers at isolated pockets.

Day 5 & 6 (Aug 5 - Aug 7): Rain likely to continue, though intensity may reduce; still a chance of heavy rain at isolated spots.

Day 7 (Aug 7 - Aug 8): IMD forecasts no major rainfall warnings, indicating a possible break in intensity.

This alert gains significance in light of the ongoing flood risks along NH 10, especially near Melli and Teesta Bazaar, where the Teesta River’s elevated riverbed continues to pose a high flood hazard. The riverbed, as per Jal Shakti Ministry findings, has risen by up to 14 metres at certain stretches due to debris and silt accumulation from the October 2023 flash flood.

In response to these developments, Lok Sabha MP from Sikkim, Dr. Indra Hang Subba, has sought urgent intervention from Union Minister Nitin Gadkari, requesting the construction of an alternative Greenfield highway and the installation of temporary elevated corridors along flood-prone sections of NH 10 to maintain connectivity and safety.

The IMD has advised residents, travelers, and district authorities to remain vigilant, particularly in vulnerable regions along riverbanks, hilly terrain, and areas with history of landslides. Continuous rainfall may trigger waterlogging, road blockages, and landslides, especially in districts like Mangan, Namchi, and Gyalshing.