Widespread Heavy Rain Expected Across Tamil Nadu and Southern States (September 18, 2025)
Good Morning from Rainman Studio! This is Venkatesh with your daily weather analysis for September 18, 2025. Please note that this is my personal weather forecast, and I advise following the official forecasts from the India Meteorological Department and government advisories.
Current Weather Systems Influencing the Region:
• An upper air cyclonic circulation previously over Central India (Maharashtra, Chhattisgarh, Jharkhand) has now moved slightly and is situated near Marathwada, an interior region of Maharashtra. This system is expected to persist for the next 24 hours before weakening.
• The upper air cyclonic circulation that was over the Andaman region has moved further east and is now located over Myanmar.
• A low-pressure area continues to prevail over the South China Sea, but it is not expected to cause significant changes to our weather.
• An anti-cyclone is present over Rajasthan, indicating the expected withdrawal of the Southwest Monsoon from the remaining parts of Rajasthan today.
• A deepening convergence system is anticipated in the Bay of Bengal around September 20th or 21st, which is likely to form a strong upper air cyclonic circulation.
• The presence of a cross-equatorial westerly burst and the Madden-Julian Oscillation (MJO) in phases 3-4 suggests the movement of strong moisture-laden winds from the equatorial region.
• A significant trough line (தாழி அமைப்பு) extends from North Interior Karnataka all the way to South Tamil Nadu, specifically up to Thoothukudi. This system is a primary reason for the expected widespread rainfall in Tamil Nadu today.
Rainfall Outlook for the Next 24-38 Hours:
Many regions are gearing up for a wet spell:
• Kerala: Widespread moderate to heavy rain is expected. Parts of Thrissur (western), Ernakulam (western), and Idukki districts may experience very heavy rainfall.
• Karnataka: Chamarajanagar district is likely to see very heavy rain. Other areas, including Bengaluru and the Cauvery catchment regions, can anticipate moderate to heavy rain.
• Andhra Pradesh: Heavy to very heavy rain is forecast for Tirupati and Chittoor. Prakasam, Nellore, Kavali, Annamayya, YSR, Mandya, Nandyal, Kurnool, and Anantapur will likely experience moderate to heavy rain. North coastal areas might see moderate rain in some pockets.
• Telangana: Rainfall may slightly decrease as the trough system moves away from Madhya Pradesh and Maharashtra. However, moderate to heavy rain is still expected in Nizamabad, Kamareddy, Medak, Hyderabad, Sangareddy, Vikarabad, Nagarkurnool, Wanaparthy, and Jogulamba. Eastern parts may see reduced rainfall.
Tamil Nadu Weather Focus:
Similar to yesterday, today's weather patterns are conducive to widespread rain across Tamil Nadu. While Chennai did not receive rain yesterday due to unfavorable steering, the conditions are more favorable today.
• Moderate Rain: Nagercoil, Kanyakumari, Tirunelveli, Tenkasi, Coimbatore, and Tiruppur districts.
• Moderate to Heavy Rain: Nilgiris, Valparai, Erode, Dindigul, Namakkal, Karur, Tiruchirappalli, Perambalur, Madurai, Sivaganga, Virudhunagar, Ramanathapuram, Thoothukudi, Pudukkottai, Mayiladuthurai, Nagapattinam, Karaikal, Tiruvarur, Thanjavur, Ariyalur. Coastal areas like Cuddalore and Pondicherry can also expect moderate to heavy rain during evening and night hours.
• Moderate to Heavy Rain (with isolated heavy falls possible): Chennai, Tiruvallur, Kancheepuram, Ranipet, Chengalpattu, Villupuram, Tiruvannamalai, Kallakurichi, Vellore, Tirupattur, Krishnagiri, Dharmapuri, and Salem districts. Real-time conditions will help predict the exact intensity for these areas.
Advisory for Farmers:
Farmers in the northern interior districts of Tamil Nadu and South Tamil Nadu are advised to postpone agricultural activities such as planting or spraying pesticides for the next two days. There is a possibility of a brief dry spell for two to three days starting from September 20th or 21st.
Stay safe and stay updated!
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