Why is Chennai like Ooty these days? Scientist S Balachandran explains

Chennai residents have experienced an unusually cool and cloudy January this year, a sharp contrast to the typically mild, clearer Januarys the city is used to after the northeast monsoon withdraws.

In an interview with The Federal, former additional director general of the Regional Meteorological Centre in Chennai, S Balachandran, explained the mix of delayed monsoon withdrawal, low-pressure systems near Sri Lanka, and stronger northerly winds that combined to make the month feel significantly “chillier” than usual.

Balachandran said January in coastal Tamil Nadu is generally moderated by the ocean, which acts as a “large heat source”, preventing extreme lows. But this year, several weather features aligned to keep skies cloudier, bring intermittent rain, and intensify wind chill — leading many residents to say it felt like “Ooty” at times.

He also addressed public concerns about whether a colder January automatically means a harsher summer, and whether such sudden shifts can be directly attributed to climate change.

A different January

Balachandran said Chennai’s usual January pattern is clear skies, relatively calmer winds, and gradually rising daytime temperatures after the northeast monsoon withdraws. “This is normally what we see in January,” he said.

Also read: Why does Chennai feel unusually cold this winter?

However, he noted that monsoon withdrawal has increasingly been “spilling over” into January in recent times. While the northeast monsoon is usually calculated across October, November, and December, he said the withdrawal date has often been delayed — sometimes extending well into mid or late January.

He pointed to recent examples where withdrawal happened on January 4 (2014), January 7 (2015), and January 4 (2016), while in other years it shifted to January 10, or even January 20–22. In 2026, he said, the withdrawal was around January 19, with spillover conditions continuing.

Winds and chill

Balachandran explained that winter conditions typically involve an anti-cyclonic pattern — generally associated with clearer skies and calmer conditions — while cyclonic systems tend to bring clouds and rain. This January, however, clouding and wind patterns were shaped by a low-pressure system that formed at a very low latitude near the Sri Lanka coast.

He said that even when such systems form far south, they can still strengthen northerly wind components over Tamil Nadu. “When it is more component from north then you will have the chillness,” he said, adding that winds made the “felt temperature” colder than what a stationary reading might suggest.

To illustrate the “felt” factor, he compared it to how a fan or moving vehicle changes how cold you feel even if the actual temperature is similar.

Cloudiness and small temperature range

A key feature this January, he said, was a reduced diurnal temperature range (DTR) — the gap between maximum and minimum temperatures in a day.

Also read: North India shivers: Snow blocks key highways in J-K, Himachal; Delhi AQI improves

Balachandran noted that on January 12, DTR was just 2.3°C, and around January 25 it was again low at 3.6°C, largely because of cloud cover and rainfall episodes. When skies remain cloudy and rain occurs intermittently, daytime temperatures don’t rise as much, while nighttime temperatures don’t fall sharply — compressing the range, but still producing a persistent “cool” feel.

He added that there were brief periods when maximum temperatures rose again (around January 15–17, touching about 30°C), before conditions shifted back with further easterly-wave influences.

What drove the cold spell?

Asked to explain the major meteorological factors simply, Balachandran said there isn’t a single cause. Chennai’s coastal climate is moderated by both the Arabian Sea and the Bay of Bengal, and the region’s proximity to the equator makes it very different from north India’s winter pattern.

This time, he said, two main features mattered:

2. A low-pressure system near Sri Lanka, which strengthened northerly wind components

He explained that winds are often a mix of components — north and east, for instance — and the balance determines whether Chennai feels more “ocean-moderated” or more “northern chill.” When winds are more easterly and ocean-origin, temperatures feel moderate; when the northerly component strengthens, chill increases — especially when combined with rain and cloudiness.

How unusual was it?

Balachandran said typical January maximum temperatures in Chennai are around 29–30°C, with minimums around 21°C. During this spell, he cited readings such as 26.8°C for the maximum and 22.6°C for the minimum, noting again that DTR and wind direction often shape how people experience the weather more than a single number.

Also read: Telangana braces for summer woes as winter retreats; IMD warns of El Nino effect

He said the coldest-feeling period was around January 12–13, when stronger northerly winds along the coast made the chill more noticeable.

Are January systems normal?

On whether low-pressure systems in January are normal, Balachandran said such systems are not unheard of, but they are not frequent. This year’s system near Sri Lanka, combined with a trough and changing wind zones, helped produce cloudiness and rainfall patterns that came in waves.

He described the rainfall as uneven — at times drizzle-like, at times more intense in pockets — with breaks between spells. This variability, he said, helped sustain a cooler feel through repeated cloud build-ups and wind shifts.

Does cold January mean hot summer?

Balachandran addressed a common worry among long-time Chennai residents: that an unusually cold January might signal a brutally hot summer.

He said the two are not automatically linked. “It need not be correlated that if winter is very chill, then automatically this will be also more,” he said. Seasonal forecasting, he explained, is done separately because each season has different “action centres” in the atmosphere that shift location and intensity over time.

He added that internal variability also plays a role, and the coming months’ maximum temperatures will depend on evolving atmospheric conditions rather than a simple winter-to-summer cause-and-effect.

Pollution and winter weather

Asked about air pollution intensifying due to winter conditions, Balachandran said pollution build-up is more likely when winds are stagnant and atmospheric mixing is weak. In Chennai, he said, conditions are different from northern latitudes, and rain and wind can help wash out pollutants.

Also read: Munnar shivers in sub-zero temperatures; tourists flock to enjoy frosty hills

He explained that dispersion depends on wind, diffusion, moisture, and sunlight-driven convection. When there is little wind and limited sunlight, vertical mixing reduces, and pollutants can accumulate near the ground. But Chennai typically does not face the same scale of winter pollution episodes as north India, though short spells can occur depending on local activities and conditions.

Climate change signals

On whether this sudden January change is a signal of climate change, Balachandran urged caution against attributing a single event directly to climate change.

He said climate change is identified when the mean state shifts over longer periods — typically 30-year averages — rather than one-off episodes. He noted that Chennai’s physical environment has changed dramatically since the mid-20th century, with differences in land use, built-up areas, and surface characteristics affecting absorption and reflection and, in turn, local conditions.

He explained that a more scientific approach looks at whether events are becoming more frequent and how they compare to historical baselines. As an example of changing rainfall character, he contrasted the 2015 Chennai rainfall event (30 cm in 24 hours) with later episodes where heavy rain occurred in shorter, more intense bursts.

Balachandran said while perceptions may label unusual weather as climate change, scientific attribution needs long-term patterns and frequency shifts — and what seems “abnormal” today could become “normal” if it repeats over several years.

(The content above has been transcribed from video using a fine-tuned AI model. To ensure accuracy, quality, and editorial integrity, we employ a Human-In-The-Loop (HITL) process. While AI assists in creating the initial draft, our experienced editorial team carefully reviews, edits, and refines the content before publication. At The Federal, we combine the efficiency of AI with the expertise of human editors to deliver reliable and insightful journalism.)