When is the Rainy Season in South Asia? - Monsoon Timing

The primary rainy season in South Asia, commonly known as the Southwest Monsoon or summer monsoon, predominantly occurs between June and September. This period brings the vast majority of the region's annual rainfall and is vital for its economies and ecosystems.

Key Phases of the South Asian Rainy Season

The timing of the monsoon is not a single event but rather a gradual progression across the subcontinent:

• Monsoon Onset: The rainy season typically begins in late May or early June. It makes its first landfall over the southern tip of India (Kerala) and Sri Lanka, as well as the Bay of Bengal.
• Advance Across the Subcontinent: From this starting point, the monsoon gradually advances northward and westward. It usually reaches Mumbai by mid-June and covers almost the entire Indian subcontinent by the first week of July.
• Peak Rainfall: The peak rainy months for most of South Asia, including India, Pakistan, Bangladesh, and Nepal, are July and August.
• Monsoon Withdrawal: The rainy season begins its retreat, or withdrawal, in early September from the northwestern regions (like Rajasthan, India, and Pakistan). It gradually withdraws from the rest of the region, typically completing its exit by mid-October.

Regional Variations in Timing

It's important to note that timing can vary:

• Northwest India and Pakistan: These regions have a shorter rainy season, often starting later (early July) and ending sooner (early September).
• Northeast India (e.g., Cherrapunji): This area receives some of the heaviest rainfall in the world, starting early (sometimes in May) and lasting the entire season.
• Southern India (Tamil Nadu) & Sri Lanka: These regions also experience a second rainy season, the Northeast Monsoon (or "retreating monsoon"), which brings rainfall from October to December.

While the core rainy season for South Asia is June to September, the exact start and end dates vary by specific location, with a general south-to-north progression during onset and a north-to-south retreat.