New Delhi: India’s southwest monsoon is in its peak stage with ISRO’s INSAT-3DR and INSAT-3DS weather satellites showing that more than 70% of the country was under cloud cover on July 21, 2026. But meteorologists say the real story is not a country’s extensive cloud cover but a greater intensity of storms emerging underneath it.
Satellite images taken from 10:45 am to 11:27 am IST and analyzed by India Meteorological Department (IMD) show towering storm systems over the Bay of Bengal, Odisha and West Bengal and very cold clouds for the morning and evening. These observations indicate thunderstorms are getting taller, stronger and producing heavy rainfall in many parts of the country.
Cloud Top Brightness Temperature Shows Storm Strength
One of the most important measurements for meteorologists is Cloud Top Brightness Temperature (CTBT). Unlike the ground-based weather instruments, satellites cannot directly measure the physical temperature of clouds. Instead, they detect the infrared radiation from the cloud tops and convert it into the temperature in an estimated form.
Because temperatures in the troposphere decrease by about 6.5 degrees Celsius per km of altitude, colder cloud tops show up in satellite images as taller storm clouds. In other words, the colder the cloud top appears in satellite images, the higher the storm has risen into the atmosphere and the greater the potential intensity.
According to the latest INSAT observations, CTBT over some parts of the Bay of Bengal, Odisha and West Bengal have dropped to between -60°C and -80°C. Such extremely low readings suggest thunderstorm towers extending 12 to 16 kilometres above the Earth's surface, and are some of the strongest convective systems currently affecting the Indian monsoon.
However, the region in central India and parts of the Gangetic plains have relatively warmer cloud top temperatures around -40°C with widespread monsoon clouds but relatively less intense convection.
Why Are These Cold Cloud Tops Important?
Colder cloud tops are closely associated with rapid upward air movement that drives heavy rainfall, thunderstorms, lightning and sometimes severe weather events, said meteorologists.
These huge cumulonimbus clouds carry huge amounts of moisture high into the atmosphere, where condensation releases latent heat and storms can keep going on in force. The latest satellite observations indicate that several active monsoon systems are still very energized over eastern India.
The results also show the utility of modern satellite technology in weather forecasting. INSAT satellites keep monitoring rapidly intensifying storms to predict them in time and to provide timely warnings to the people of the country and improve the weather forecast.
What Does This Mean for Delhi?
The most intense storm systems are concentrated in eastern India and Delhi is also experiencing the effects of the evolving monsoon pattern.
The monsoon trough, a low-pressure zone responsible for steering rainfall across northern India, has recently shifted and now extends through the national capital after being relatively inactive for several days.
Because of this, some parts of Delhi-NCR received light rainfall on Tuesday morning, which brought relief from humid conditions. The IMD issued a Yellow Alert for Delhi and predicted:
- Generally cloudy skies
- Light to moderate rainfall
- Isolated heavy showers
- Thunderstorms
- Gusty winds over the next two days
Residents should monitor official weather updates and watch for weather via the official weather update during periods of heavy rainfall and thunderstorms.
Water Vapour Images Show Moisture Supply
Besides infrared cloud temperature data, the INSAT-3DS satellite also provides water vapour channel images at 6.88 micrometres, allowing meteorologists to see moisture distribution in the middle and upper atmosphere.
The latest imagery shows a wide zone of moisture across northern and central India into the Bay of Bengal. This abundant atmospheric moisture continues to feed developing thunderstorms over eastern India.
However, relatively dry air dominates much of the Arabian Peninsula and western Pakistan, implying that the current monsoon moisture supply remains largely unaffected from the western side.
Active Monsoon Expected to Continue
The IMD says that active monsoon conditions are likely to continue over northwest and northeast India during the next four to five days. Heavy to very heavy rain will be observed over Odisha, Chhattisgarh and adjoining regions and in the areas that are currently experiencing the coldest cloud top temperatures.
Although cloud cover could vary from day to day as storm systems develop and weaken, meteorologists predict that the monsoon will be more intense in general.
The latest observations from ISRO's INSAT satellites reflect the way advanced space monitoring techniques have emerged as an indispensable tool to understand India’s complex weather systems.
Scientists can now monitor cloud-top temperatures, moisture patterns and storm development in near real time in order to better anticipate severe weather events and help authorities issue timely warnings.
As the monsoon continues to take hold in the area of the monsoon, we encourage residents in the affected areas to be on alert, to monitor the situation and follow IMD advisories, and to take precautions during periods of heavy rainfall, thunderstorms, and strong winds.
