The monsoon season has officially kicked off across parts of Asia, bringing the kind of rainfall that makes umbrella manufacturers weep with joy and farmers breathe sighs of relief. The south-west monsoon, a meteorological marvel driven by the growing temperature difference between the Asian landmass and the Indian Ocean, is now in full swing. As the land heats up faster than the sea each spring, it creates a pressure difference that sucks moisture-laden ocean air inland, where it rises, condenses, and dumps rain like it’s trying to settle a grudge.
This self-sustaining feedback loop - where condensation releases heat, reinforces low pressure, and draws in even more ocean air - keeps the system chugging along like a well-oiled weather machine. The Somali Jet, a wind off the east African coast, acts as a continuous moisture pipeline across the Arabian Sea into the Indian subcontinent. The monsoon eventually retreats in autumn when the land cools and the temperature contrast fades, leaving everyone to dry out.
India declared the official onset of its monsoon season on 4 June in its far south-western Kerala region, three days later than the average start of 1 June - because even weather can be fashionably late. The system has since advanced north-east into Karnataka and Andhra Pradesh. Coastal stations in Kerala recorded up to 280mm (11in) of rain in just 72 hours between 4 and 7 June, roughly half of London’s average annual rainfall, which seems like a lot unless you’re a Londoner used to drizzle. Models on Sunday indicated another 200-250mm for the region this week, with red warnings issued for extremely heavy rainfall, flash flooding, and landslides.
This monsoon onset is vital for agriculture across India, as farmers of rain-fed crops like rice and cotton need to plant early, knowing the risk of prolonged dry spells has passed. Farther east, Thailand’s 2026 monsoon season began on 15 May, with up to 1,000mm of rain recorded locally in the south-west and another 300mm possible within the next week. The Thai meteorological department has warned that strong monsoon winds over the Andaman Sea could generate waves of 2 - 3 metres, advising small vessels to stay ashore - a polite way of saying, “Don’t be an idiot in a boat.”
Despite the early downpours, the season as a whole is forecast to be below normal. India’s meteorological department projects rainfall totals between June and September at about 90% of the long-period average, partly due to El Niño conditions expected to develop and strengthen as the season progresses. So, while the monsoon is here, it might be a more restrained version - think of it as monsoon lite.