New Delhi, May 13 -- Southwest monsoon is likely to make onset over some parts of Andaman Sea, South Bay of Bengal and Andaman and Nicobar Islands by Tuesday, over a week ahead of the normal date for advance of monsoon over the region, India Meteorological Department said on Monday. The normal date for advance of monsoon over Andaman region is May 21, as per IMD's New Normal Dates of Onset/Progress and Withdrawal of Southwest Monsoon over India released in 2020. There is fairly widespread rainfall with isolated heavy rainfall recorded over the Nicobar Islands during past 24 hours. Rainfall activity over Nicobar islands is very likely to increase becoming widespread rainfall with isolated heavy to very heavy rainfall during next 24 hours, IMD said adding: "With expected continuance of rainfall activity over these areas, conditions are favourable for advance of southwest monsoon into some parts of Andaman Sea, South Bay of Bengal and Andaman & Nicobar Islands by tomorrow, the 13th May, 2025." Conditions are also becoming favourable for further advance over some parts of south Arabian Sea, Maldives, Comorin area; some more parts of South Bay of Bengal, entire Andaman and Nicobar Islands and Andaman Sea; and some parts of central Bay of Bengal during subsequent 4-5 days, IMD said. "There is a cyclonic circulation over southeast Bay of Bengal due to which rain activity will intensify. Rainfall is increasing and conditions are gradually becoming favourable for onset of monsoon. A heat low will be created and monsoon may reach parts of Arabian Sea in the next 4-5 days," said Mahesh Palawat, vice president, climate and meteorology, Skymet Weather. Heat wave conditions are likely to continue over some areas of West Bengal till May 15 and likely to commence over Jharkhand from May 13, over Uttar Pradesh from May 14 and over West Rajasthan from May 15. Widespread light to moderate rainfall with heavy to very heavy rainfall likely over Nicobar Islands on May 13. Rainfall accompanied with thunderstorms and lightning likely to continue over West, Central & South Peninsular India during next 5 days. Heavy to very heavy rainfall accompanied with thunderstorms and lightning is also likely over Northeast India during next 5 days. A western disturbance as a cyclonic circulation is over Punjab in lower levels with trough aloft trough in middle tropospheric westerlies. An upper air cyclonic circulation lies over northwest Uttar Pradesh and another over West Rajasthan and neighbourhood in lower tropospheric levels. A trough is running from central parts of Bihar to south Jharkhand in lower tropospheric levels. A trough is also running from Saurashtra to eastcentral Arabian Sea across North East Arabian Sea. The upper air cyclonic circulation over Northeast Ass- am and neighbourhood in lower and middle tropospheric levels. Under the influence of these systems, light to moderate rainfall with thunderstorm, lightning and gusty winds speed reaching 40-50km/hour gusting to 60km/hour is likely over Jammu-Kashmir-Ladakh-Gilgit-BaltistanMuzaffarabad; Punjab, Haryana Chandigarh and Delhi, East Rajasthan on May 13; Himachal Pradesh during May 16 to 17; with winds speed reaching 30-40 kmph gusting to 50km/hour over Himachal Pradesh; Jammu-Kashmir-Ladakh-Gilgit- Baltistan-Muzaffarabad on May 14. Over west India, light/moderate rainfall accompanied with thunderstorm, lightning and gusty winds speed reaching 40-50 kmph gus- ting to 60 kmph likely over Gujarat; Konkan and Goa on May 13 and 14; Madhya Maharashtra, Marathawada during May 14 to 16; thundersquall wind speed reaching 50-60 kmph gusting to 70 kmph likely over Madhya Maharashtra, Marathawada on May 13....