India’s September 2025 temperature anomaly was shaped not by blazing afternoons but by unusually hot nights, according to the India Meteorological Department’s (IMD) monthly climate summary released on October 8. The report revealed that the night-time temperature anomaly — rather than daytime heat — was the primary driver behind the country’s above-average temperatures.

Nights Warmer Than Ever

Across India, the average minimum temperature in September 2025 was 23.44°C, which is 0.63°C higher than the long-term normal of 22.80°C (1991–2020). Meanwhile, the mean temperature — the daily average of maximum and minimum — stood at 27.51°C, 0.39°C above its normal.

In contrast, the average maximum temperature was 31.58°C, just 0.15°C above the normal, showing that it was the night-time warmth, more than daytime heat, that caused the temperature anomaly. These elevated minimum and mean temperatures make September 2025 one of the warmest months on record for night conditions in India.

September 2025 Temperature Anomaly Overview: September 2025 (India)

Source: India Meteorological Department (IMD)

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Warm Nights Across Indian Cities

An analysis of Down To Earth’s daily “heat tracker” data revealed that half of 35 monitored cities recorded 20 or more days of above-normal minimum temperatures — meaning over 65% of September nights were unusually warm.

The cities most affected included Diu (29 nights above normal), followed by Patna, Srinagar, and Lucknow (26 nights each). Other cities such as Jammu, Dehradun, Guwahati, Ranchi, Jaipur, and Kolkata also experienced prolonged warm nights.

In contrast, only 10 cities saw above-normal daytime maximum temperatures, reinforcing that the night-time temperature anomaly was the dominant factor behind the month’s warmth.

Regional Highlights

The east and northeast regions experienced some of the most pronounced anomalies. The average minimum temperature in this region was 24.52°C, 0.82°C above normal, ranking as the third-highest since 1901. Meanwhile, the average maximum temperature of 32.31°C, 1.59°C above normal, also ranked third-highest for the region — indicating that both day and night were unusually hot.

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The Broader Climate Signal

The IMD’s findings point to a worrying trend — the warming of nights is accelerating faster than daytime temperatures across India. Night-time heat poses unique health and environmental challenges, disrupting sleep, reducing recovery from daytime heat stress, and straining urban cooling systems.

As the planet continues to warm, understanding and addressing such nocturnal temperature patterns will be key to future climate adaptation strategies.

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