A low pressure system over the southeast Bay of Bengal and the Andaman and Nicobar Islands region is expected to intensify into a cyclonic storm within the next 24 hours, raising the prospect of heavy rainfall across parts of Tamil Nadu over the coming days.

The Meteorological Department has forecast rain in several regions of the state for the next three days as the developing weather system strengthens over the Bay of Bengal. The immediate outlook points to moderate rainfall across northern coastal districts, areas along the Western Ghats and several interior parts of Tamil Nadu.

The weather threat is building again. Authorities are closely tracking the system.

On Sunday, moderate rainfall is expected in Tamil Nadu's northern coastal belt and districts along the Western Ghats. Similar weather conditions are forecast in Madurai, Tiruchirappalli, Namakkal, Salem, Erode and Karur, while several other parts of the state may receive light showers at isolated locations.

The rainfall pattern is expected to remain uneven, with some districts facing more intense spells than others. Nilgiris and Tiruvallur are among the districts likely to receive heavy rain on Monday. Cuddalore and Villupuram could experience heavy showers through Tuesday as the impact of the developing Bay of Bengal system becomes more pronounced.

The forecast places particular attention on northern Tamil Nadu and the Western Ghats districts, where moderate rainfall is likely at isolated places during the forecast period. Other regions may receive light to moderate rain depending on the movement and intensity of the weather system.

In Chennai, the skies are expected to remain partly cloudy on Sunday, with light to moderate rainfall possible in some parts of the city. Thunderstorms and lightning could accompany the showers, adding to concerns over sudden changes in local weather conditions.

The forecast does not indicate continuous rainfall across Chennai. Instead, residents could see localised showers, meaning some neighbourhoods may receive significant rainfall while other areas remain comparatively dry.

The district wise outlook shows a gradual increase in rainfall intensity. Moderate rain is expected to dominate the initial phase of the forecast before heavier spells affect selected districts from Monday. Nilgiris and Tiruvallur are expected to be among the first areas facing the possibility of heavy rain, followed by Cuddalore and Villupuram.

The developing cyclonic system remains the central factor behind the latest weather warning. A low pressure area can strengthen rapidly over the warm waters of the Bay of Bengal, and meteorological agencies will continue monitoring its movement, intensity and potential impact on coastal areas.

For Tamil Nadu, the immediate concern is heavy rainfall rather than a uniform weather event across the entire state. Northern coastal districts, the Western Ghats and selected interior regions are expected to remain under closer watch as the system develops.

Residents in areas covered by the heavy rain forecast may need to prepare for waterlogging, difficult travel conditions and thunderstorms. Lightning activity could also create additional risks during intense spells of rain.

The next 24 hours will be significant. The expected intensification of the low pressure system into a cyclonic storm will determine how weather conditions evolve across Tamil Nadu and nearby coastal regions.

With rain already forecast across multiple districts and heavier spells expected in selected areas, the state is preparing for another period of unsettled weather linked to the increasingly active Bay of Bengal system.