The South West Monsoon (SWM) brings more than 75 per cent of India’s rainfall between June and September. But it is characterised by break periods within that period when rains stop in most of the country and increase in the foothills of the Himalayas and the Northeast.
These monsoon break periods are caused by dry winds that flow from the west and northwest of India and can be predicted beforehand to create better early warning systems for dry periods during the SWM, according to a new research paper published in the Journal of Climate on February 10, 2026. Such early warning systems can be used by farmers dependent on monsoon rainfall to plan their agricultural activities.
The scientists from University of Reading and United Kingdom’s Met Office in Exeter analysed data on 188 monsoon break periods between 1940 and 2023 to understand the correlation between the occurrence of dry western winds and monsoon break periods.
When a break in the SWM season occurs the main monsoon trough moves from its normal position over the Indo-Gangetic plains to the foothills of the Himalayas which reduces the rainfall over central India.
The most recent major break period in the SWM was in the early part of the season in 2024. The Bay of Bengal branch of the incoming monsoon trough stalled on May 31 and was in that phase for multiple weeks. The Arabian Sea branch of the monsoon trough also stalled on June 10 and remained halted for a couple of weeks. Due to this stalling between June 1 and June 18, there was a 20 per cent deficit in rainfall throughout the country, putting kharif season agricultural sowing at risk.
In July 2002, there were two severe breaks in the monsoon that led to a monthly rainfall deficit of 50 per cent in turn triggering severe drought that reduced the country’s GDP by two per cent. In 1972, the monsoon season suffered from an extended break of 17 days.
Generally, the monsoon break periods can last from a few days to a couple of weeks. The researchers found that the dry winds or dry intrusions start flowing into the country around a week before the middle day of the duration of the monsoon breaks. They reach their peak activity over northwest India and eastern Pakistan two to three days before the middle day of the monsoon breaks. The study found that extended breaks, like the one that occurred in 2024, have stronger dry winds as triggering events.
The vertical profiling of the dry intrusions revealed that there are occurring at the middle level of the atmosphere which are similar to the dry winds that drive the direction of the withdrawal of the SWM from the Indian subcontinent in late September and early October. The winds originate in remote dry regions towards the west of the Hindu Kush mountains and close to the border of Afghanistan, Iran and Turkmenistan flowing through gaps in the terrain.
“As breaks evolve, these dry intrusions deepen throughout their horizontal extent and descend into the country, stabilizing the troposphere and creating an unfavourable environment for deep convection,” wrote the authors. This stabilisation of the troposphere is the meteorological cause of the monsoon break.
The maximum number of breaks occur in August, followed by July, September and June and the average duration of the 188 identified breaks was 5.7 days, according to the paper. The researchers identified the middle day of the break based on whether the duration was even or odd.
For odd number of days, the middle day was chosen such as for five days the third day and for even number of days such as four days, the day with the least rainfall over the core monsoon zone among the second or third day. The core monsoon zone is a contiguous area from northwest of the country to some eastern regions where agriculture is still mostly rain-fed.
The scientists defined short breaks as three days or less and extended breaks as seven days or more. This gave them a total of 56 short breaks and 54 extended breaks between 1940 and 2023. “The core monsoon zone receives significantly less rainfall on the middle day of extended breaks compared to short breaks, with precipitation remaining below 2 mm per day for a longer duration,” according to the paper.
For short breaks the peak strength of the dry winds is on the middle day and for extended breaks this maximum activity of dry intrusion is 3-5 days before the middle day, as per the paper. “The impact of the dry intrusion weakens gradually in the days following the middle day of breaks, and precipitation over the core monsoon zone increases,” wrote the study authors. “Strong dry intrusions increase the duration of breaks, whereas the frequency of breaks decreases as the strength of dry intrusions increases,” they added.
The scientists further concluded that this causal relationship between dry winds coming from the west and northwest and the break periods in the SWM can be used to design and implement early warning systems for farmers.
“When these air masses arrive, crops can wither in the fields and water supplies can run low for more than a billion people. By tracking these flows as they build up days before they reach India, we can give farmers and communities precious time to prepare for the dry spell ahead,” said Akshay Deoras, the lead author of the paper and research scientist at the University of Reading in a press release.
“The team developed a novel index, which could help weather forecasters spot dry air before it arrives in India. This would give farmers time to manage agricultural activities, water managers time to restrict supplies, and communities time to prepare for water shortages days before the rains stop,” according to the press release.