Why is it raining in Delhi for the third day in a row? The reason is invisible

Delhi woke to rain again on July 22, the third morning in a row, and the third morning of a city that no longer feels like the one it was last week.On July 19, the afternoon touched 38 degrees Celsius. By July 21, the IMD had recorded a fall of 5 to 7 degrees in a single day.Rain has fallen across Delhi and its suburbs through the morning, with the heaviest spells in pockets of the city. Official station figures are due later in the day.None of this is one storm. It is an entire system rearranging itself over northern India, and most of it is happening where nobody can see it. WHY IS IT RAINING SO MUCH IN DELHI TODAY?Because the monsoon trough came home.The monsoon trough is a long belt of low pressure lying across northern India through the rainy season, and it is the most important line on any Delhi forecast.Low pressure means air is being drawn in from every side, and air being drawn in has only one direction left. Up. Rising air cools, moisture condenses, rain falls.When the trough drifts north and parks against the Himalayan foothills, Delhi sits on the sinking side of it, humid and grey and dry. IMD's bulletin of July 21 places it near its normal position, back over the plains.WHAT IS A CYCLONIC CIRCULATION, AND HOW DOES IT CAUSE RAIN?The trough is not working alone. IMD is tracking five spinning columns of air, called upper air cyclonic circulations, over Haryana, southwest Rajasthan, northeast Madhya Pradesh, north Chhattisgarh and the west-central Bay of Bengal.A cyclonic circulation is not a cyclone. It is a slow vortex sitting a kilometre or more above the ground, which is exactly why you will not find it on a surface map. It works like a pump, drawing damp air inwards and lifting it.One of them is in Haryana. That is next door.WHERE IS DELHI'S RAIN ACTUALLY COMING FROM?Both seas at once.IMD describes a trough running from the west-central Bay of Bengal all the way to the northeast Arabian Sea. On July 21, it reached down from the middle of the atmosphere into the lower levels, and that matters, because the lower atmosphere is where the moisture actually sits.Delhi's winds have swung to the southeast. Easterlies are the signature of Bay of Bengal moisture travelling overland across the Gangetic plains. Chunar in Mirzapur logged 19 cm in a day. Palwal, an hour from Delhi, logged 7 cm.WHY DOES DELHI FLOOD WHEN THE RAIN IS NOT EXTREME?Because the ground has stopped absorbing. Water a field would swallow runs off concrete and tarmac into drains built for a smaller, greener city. IMD's impact note lists localised road flooding, waterlogging in low-lying areas and closed underpasses.The meteorology is ordinary. The plumbing is not.HOW LONG WILL THE RAIN IN DELHI LAST?The IMD expects fairly widespread to widespread rain over Haryana, Chandigarh and Delhi until July 23, with isolated heavy falls on July 22 and 23, easing to scattered showers from July 24. Check the district warnings before you leave home.Then the trough will move again. It always does.- EndsPublished By: Radifah KabirPublished On: Jul 22, 2026 10:05 IST