Mumbai's climate is defined by its coastal position on the Arabian Sea, resulting in a tropical wet and dry climate (Köppen: Aw). The city is characterized by extreme seasonality, particularly regarding rainfall, and a high level of humidity that persists throughout much of the year.
Seasonal Rhythm
The Monsoon (June to September)
The arrival of the southwest monsoon in early June is a transformative event. During these four months, Mumbai receives over 85% of its annual precipitation, often in torrential bursts that can drop hundreds of millimeters of rain in a single day.
- Atmosphere: The sky is dominated by heavy, low-hanging clouds. While temperatures dip slightly to the high 20s°C (70s-80s°F), the humidity peaks at an oppressive 85% or higher.
- Feeling: The air feels heavy and water-logged. Locals refer to this as the city's "romantic" but chaotic season, where the scent of wet earth (petrichor) competes with the practical challenges of urban flooding.
Post-Monsoon and "October Heat" (October to November)
As the rains retreat, Mumbai experiences a sharp spike in temperature and humidity.
- The Phenomenon: Known locally as "October Heat," this period can feel more uncomfortable than the peak of summer. The clear skies allow for intense solar radiation, while the residual moisture in the ground creates a "sauna effect."
- Feeling: Expect a high heat index where 32°C (90°F) feels like 38°C (100°F) due to the stagnant, humid air.
Winter (December to February)
This is widely considered the most pleasant time in the city.
- Patterns: Skies are clear and blue. Daytime temperatures hover around 30°C (86°F), but nights can drop to a refreshing 18°C (64°F).
- Feeling: The air is significantly drier, and the cool sea breezes are most prominent during the evenings, making outdoor activities across the Marine Drive promenade popular.
Summer (March to May)
Temperature and humidity steadily climb throughout this period.
- Trends: May is typically the hottest month, with temperatures occasionally reaching 38°C-40°C (100°F-104°F).
- Feeling: The heat is relentless. The city feels hazy, and the "feels like" temperature remains high even after sunset because the Arabian Sea acts as a heat sink, preventing the city from cooling down rapidly at night.
Daily Climate Behavior
Mumbai’s weather is governed by the Land and Sea Breeze cycle.
- Daytime: As the land heats up, a cooler sea breeze moves in from the Arabian Sea, usually in the late morning or early afternoon. This provides a natural (though humid) cooling effect for coastal areas like Colaba and Worli.
- Nighttime: The cycle reverses, with a land breeze blowing toward the sea. In the urban core, however, the Urban Heat Island (UHI) effect often traps heat between high-rise buildings, meaning internal neighborhoods may stay significantly warmer than the coast.
Microclimates and Variations
Despite being a single metropolis, Mumbai has distinct microclimates:
- Coastal vs. Inland: South Mumbai (Colaba) and coastal suburbs (Juhu, Bandra) stay more moderate due to the sea. Inland suburbs like North Mumbai, Thane, and Kalyan often experience temperatures 2°C to 5°C higher in summer and lower in winter.
- Green Pockets: Areas near the Sanjay Gandhi National Park or Powai can be noticeably cooler (sometimes by up to 10°C) than densely packed industrial or commercial zones like Ghatkopar or Dharavi.
Local Adaptation and Phenomena
- Resilience: Mumbaikars are famous for their monsoon resilience. The city rarely stops for rain, with locals using "monsoon gear"—sturdy umbrellas and waterproof footwear—to navigate waterlogged streets.
- Cyclones: While historically rare, Mumbai has recently seen an increase in tropical cyclone activity in the Arabian Sea during the pre-monsoon (May) and post-monsoon (November) periods.
- Tides: Locals pay close attention to the "High Tide" schedule during monsoon months; if a high tide coincides with heavy rain, the city's drainage system cannot empty into the sea, leading to immediate urban flooding.