Chennai experiences a tropical wet‑and‑dry climate with consistently high temperatures, a pronounced monsoon from October to December, and relatively mild winters. The city’s average annual temperature is about 28 °C (82 °F), while humidity often exceeds 70 % in the summer months.
According to the Köppen climate classification, Chennai falls under the “Aw” category, meaning a tropical savanna climate with a distinct dry season. This classification explains why the city sees a clear division between a hot, dry period (March‑May) and a wet, cooler period (October‑December).
During the peak summer months of April and May, daily maximum temperatures regularly climb to 38‑40 °C (100‑104 °F). Historical records show the all‑time high reaching 42.5 °C (108.5 °F) on 2 May 2017. Nighttime lows rarely drop below 26 °C (79 °F), making evenings feel warm as well.
The northeast monsoon, locally called “Retreating Monsoon,” arrives in early October and peaks in early November. Chennai receives about 1,200 mm (47 in) of rain annually, with more than 70 % falling during the monsoon months.
| Month | Avg. Rainfall (mm) | Avg. Max Temp (°C) |
|---|---|---|
| Oct | 265 | 31 |
| Nov | 235 | 30 |
| Dec | 110 | 30 |
| Jan | 20 | 29 |
| Feb | 15 | 30 |
| Mar | 10 | 33 |
| Apr | 5 | 38 |
| May | 5 | 40 |
Travelers seeking pleasant conditions should target January through March. During this window, average highs stay between 28‑30 °C (82‑86 °F) and humidity drops to 60‑65 %, providing a more manageable climate for sightseeing and outdoor activities.
High humidity amplifies the perceived temperature, a phenomenon known as the heat index. For example, a 35 °C (95 °F) day with 80 % humidity feels like 42 °C (108 °F). Residents mitigate this by using air‑conditioned homes, staying hydrated, and scheduling outdoor work for early mornings.
While all three cities—Chennai, Mumbai, and Kolkata—experience tropical climates, Chennai’s dry season is longer, and its monsoon occurs later in the year. Mumbai’s southwest monsoon peaks in June‑July, and Kolkata sees heavy rainfall from July‑September.
| City | Peak Summer Max (°C) | Monsoon Months | Annual Rainfall (mm) |
|---|---|---|---|
| Chennai | 40 | Oct‑Dec | 1,200 |
| Mumbai | 35 | Jun‑Sep | 2,400 |
| Kolkata | 36 | Jul‑Oct | 1,800 |
Relative humidity stays high throughout the year, but it peaks during the monsoon. The monthly average ranges from 55 % in January to 85 % in November. High humidity combined with warm temperatures raises the heat index, especially in the pre‑monsoon months of April and May.
| Month | Avg. Humidity (%) |
|---|---|
| Jan | 55 |
| Feb | 58 |
| Mar | 68 |
| Apr | 78 |
| May | 80 |
| Jun | 78 |
| Jul | 82 |
| Aug | 84 |
| Sep | 86 |
| Oct | 88 |
| Nov | 90 |
| Dec | 85 |
Chennai lies on the Bay of Bengal, making it susceptible to cyclonic storms, especially between October and December. Notable events include Cyclone “Nisha” (2008) and Cyclone “Vardah” (2016), which caused coastal flooding and wind gusts above 120 km/h. Early warning systems and improved drainage have reduced casualties, but property damage remains a risk.
Long‑term data from the Indian Meteorological Department shows a gradual rise in average temperature—about 0.2 °C per decade since 1980. Sea‑level rise of approximately 3 mm per year has increased the frequency of tidal flooding during high tides. Experts predict more intense but shorter monsoon bursts, raising the probability of flash floods.
Because Chennai is close to the equator, daylight hours vary little across the year. Sunrise occurs between 5:45 am (December) and 6:10 am (June); sunset ranges from 6:00 pm (June) to 6:30 pm (December). These consistent daylight periods are useful for planning outdoor activities.
| Month | Sunrise | Sunset |
|---|---|---|
| Jan | 6:05 am | 6:20 pm |
| Apr | 6:10 am | 6:15 pm |
| Jul | 5:45 am | 6:00 pm |
| Oct | 5:55 am | 6:25 pm |
During summer, a south‑west monsoon wind known locally as the “sea breeze” develops after 10 am, bringing cooler air from the Bay of Bengal. Temperatures often drop 2‑3 °C (3‑5 °F) between 2 pm and 5 pm, providing brief relief before the evening humidity rises again.
The lowest temperature on record is 16.5 °C (61.7 °F), observed on 4 January 1942. Nighttime lows in recent decades usually stay above 19 °C (66 °F), reflecting the city’s overall warm climate.
Chennai’s coastal location helps disperse pollutants, but during the dry pre‑monsoon period, stagnant air can lead to higher PM2.5 concentrations. The Tamil Nadu Pollution Control Board reported an average annual PM2.5 level of 45 µg/m³ in 2022, exceeding the World Health Organization’s safe limit of 10 µg/m³. Rainfall during the monsoon typically clears the haze, lowering particulate matter by up to 60 % within a few days.
Residents often check the real‑time AQI app before planning outdoor workouts.
Overall, Chennai’s weather is defined by predictable seasonal cycles, high humidity, and occasional extreme events. By consulting reliable forecasts and understanding these patterns, residents, tourists, and planners can make informed decisions about daily activities, infrastructure, and travel itineraries.
The coolest period is from January through March. During these months average high temperatures stay between 28 °C and 30 °C (82‑86 °F) and humidity falls to 60‑65 %, making outdoor sightseeing and evening walks comfortable. Hotel rates are also lower and the city hosts several cultural festivals such as the Pongal harvest celebration.
Chennai is located near the equator, so temperatures rarely drop below 15 °C (59 °F) even at night. The city has never recorded snowfall, and any frost is virtually impossible because sea temperatures stay above 25 °C year‑round. During the winter months the sky remains clear, and visitors enjoy mild evenings perfect for beach walks.
Cyclones affect Chennai mainly between October and December, when the northeast monsoon creates favorable conditions. Since 2000, the city has experienced several notable cyclones, including Nisha in 2008 and Vardah in 2016, both producing wind speeds over 120 km/h and coastal flooding.
Daily temperature swings in Chennai are relatively small because of its maritime influence. In summer, daytime highs often reach 40 °C while nighttime lows stay around 33 °C, a difference of about 7 °C. In winter, highs are near 29 °C and lows around 22 °C, a 7 °C range as well.
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