Andaman and Nicobar Islands: Climate

1.1 What Kind of Climate the Islands Have

• Climate type: the Andaman and Nicobar Islands have a humid, tropical coastal climate. Meteorologists call it Koppen type Am, a tropical monsoon climate.
• Where they sit: the islands lie in the Bay of Bengal, roughly between 6°45′N and 13°41′N. That position near the equator mostly drives the climate.
• Steady temperatures: daily temperatures rarely rise above 31°C or fall below 22°C. The mean annual temperature stays around 26-27°C, one of India’s smallest seasonal swings.

2.1 Why There’s No Real Winter

• No true winter: unlike most of India, the islands have no real winter season. Temperatures stay warm and largely stable all through the year.
• High humidity: relative humidity averages 70-85% year-round, rarely dropping below 60%, thanks to the surrounding sea.
• The sea’s effect: the warm ocean around the islands smooths out temperature swings, giving them a far steadier climate than most of mainland India.

3.1 The Southwest Monsoon Arrives First

• Timing: the Southwest Monsoon reaches the islands in late May, and stays active through September. June brings the heaviest rain.
• Earliest in India: rain usually reaches Port Blair around 20 May. That’s the earliest monsoon onset anywhere in Indian territory — 10 to 12 days before it reaches Kerala.

Worked example: picture the monsoon as a wave sweeping in from the southwest. The Andaman and Nicobar Islands stick furthest out into that wave’s path. So they get hit first, nearly two weeks before the Kerala coast.

4.1 Rain From the Northeast Monsoon Too

• A rare pattern: unlike most of mainland India, these islands also get real rain from the Northeast Monsoon. That rain falls October through December.
• Just two regions: most of mainland India dries out in winter, except Tamil Nadu’s east coast. These islands are the only other Indian region where the Northeast Monsoon brings serious rain.
• The handover: the Southwest Monsoon usually pulls back from the islands by late September. Soon after, the Northeast Monsoon begins its own run.

5.1 Why Two Monsoons Reach These Islands

• Close to the equator: the islands sit near the equator. This lets the equatorial trough and the Inter-Tropical Convergence Zone reach them as it shifts with the seasons.
• A warm sea nearby: the Bay of Bengal around the islands stays above 28°C all year. That keeps the air moist and unstable, ready to release rain.
• Sea over land: the islands are small. So the sea around them shapes the local climate far more than the land does. Hills on the bigger islands add a small extra boost of rain on their windward slopes.
• Cyclone season overlap: April-May and October-December are also peak cyclone windows here. Even when a cyclone’s path misses the islands, its rainbands still bring heavy rain.

6.1 How Rainfall Varies by Station and Season

• Annual total: rainfall ranges from about 3,000 mm to 3,500 mm a year. The exact amount depends on the station.
• Peak season: peak rainfall runs May through December, not December through May. Only February and March stay comparatively dry.
• North versus south: the northern Andamans peak with the Southwest Monsoon. The southern Nicobars peak slightly later, with the Northeast Monsoon.
• By station: Port Blair averages about 3,180 mm a year, wettest in June. Car Nicobar and Hut Bay average higher, around 3,440-3,500 mm, wettest in November. Mayabunder, in the north Andamans, averages about 3,300 mm a year.

8.1 Cyclone and Climate-Change Risk

• Two cyclone seasons: the Bay of Bengal near the islands sees two cyclone seasons each year. These fall in April-May and October-December.
• Warming seas: sea-surface temperatures around the islands have risen about 0.7-0.9°C since 1950. Marine heatwaves in 2016 and 2020 caused coral bleaching, threatening the reef system that much of the islands’ marine life depends on.
• Sea-level risk: these are low-lying islands. Rising seas put them at risk, threatening coastal towns and fresh water supplies.
• A lasting scar: the 2004 Indian Ocean tsunami, caused by an undersea earthquake, wrecked parts of the islands. It changed some coastlines and land heights for good.

9.1 The Forests This Climate Supports

• Highest forest cover: about 86% of the islands’ land is forested. That’s the highest forest share of any Indian state or Union Territory.
• What grows there: high rainfall and humidity support tropical evergreen and semi-evergreen forests, similar to the Western Ghats and the Northeast.
• Coastal mangroves: mangrove forests cover roughly 600 sq km of estuaries and tidal creeks, buffering the coast against storm surges.
• Unique species: high rainfall, isolation, and steady temperatures together help many species found only here to thrive.

10.1 Early Monsoon Onset (2026)

• The forecast: the IMD forecast an early southwest monsoon onset over the Andaman Sea and islands. It expected this by mid-May 2026, five to six days ahead of the normal schedule. (Source: Free Press Journal)
• Confirmed: by 16 May 2026, the IMD confirmed the monsoon had reached the entire Nicobar Islands. It had also reached the Andaman Sea and parts of the Bay of Bengal.
• A wider concern: despite the early onset, the IMD flagged a below-normal rainfall risk nationally this year, linked to developing El Nino conditions in the Pacific.