Chittagong, officially known as Chattogram, experiences a tropical monsoon climate characterized by high temperatures, heavy seasonal rainfall, and significant humidity. Located between the coast of the Bay of Bengal and the Chittagong Hill Tracts, the city’s weather is shaped by its maritime proximity and its topographical transition from sea to hills.
Seasonal Weather Patterns
The climate is divided into four primary seasons, each defined by the shifting winds and moisture levels of the Indian Ocean:
- Winter (December – February): This is the most stable and comfortable period. Skies are generally clear, and rainfall is minimal. Daytime temperatures average a pleasant 25°C to 27°C (77°F to 81°F), while nights are cool, often dropping to 13°C to 15°C (55°F to 59°F). Humidity is at its annual low, making the air feel crisp compared to the rest of the year.
- Summer / Pre-Monsoon (March – May): As the sun moves north, heat builds rapidly. Temperatures frequently peak in April and May, often exceeding 35°C (95°F). This season is also marked by increasing humidity and the arrival of the "Kalbaishakhi" (Nor'westers)—sudden, violet afternoon thunderstorms that bring brief relief from the heat but can be accompanied by high winds and hail.
- Monsoon (June – September): The dominant weather feature for Chittagong. The city is one of the wettest in Bangladesh, receiving a staggering 3,000mm of annual rainfall, most of which falls during these months. Constant cloud cover, heavy persistent downpours, and humidity levels between 80% and 90% are standard. While the rain cools the air to around 28°C (82°F), the high moisture content creates a heavy, oppressive feel.
- Post-Monsoon (October – November): A transitional phase where the rains taper off. The air remains humid, but temperatures begin to moderate. This period is also the secondary peak for tropical cyclone activity in the Bay of Bengal.
Daily Climate Rhythms
During the dry winter months, the day follows a predictable pattern of cool mornings, bright sunny afternoons, and a sharp temperature drop after sunset. In the summer, the heat peaks around mid-afternoon, often culminating in the build-up of massive cumulus clouds. During the monsoon, the concept of a "daily cycle" often disappears, replaced by gray skies that can persist for several days, with rain falling at any hour.
Microclimates and Regional Variations
Chittagong’s geography creates distinct local variations:
- Coastal vs. Inland: The Patenga coastal area is generally move breezy and slightly cooler during the day due to the sea breeze, but it stays warmer at night as the water retains heat.
- The Hill Tracts: Moving east toward the hills, the terrain causes orographic lift, which can lead to even higher localized rainfall than in the city center. Night temperatures in the valleys of the Hill Tracts are often several degrees lower than in the urban areas.
- Urban Heat Island: Like many rapidly growing cities, central Chittagong experiences an urban heat island effect, where concrete and high density trap heat, keeping the city 2°C to 3°C warmer at night than the surrounding rural outskirts.
Historical Context and Phenomena
Historically, Chittagong has been vulnerable to extreme weather events. The city lies in the direct path of tropical cyclones originating in the Bay of Bengal. Major cyclones, such as those in 1970 and 1991, have left deep marks on the region’s history. Locals are highly attuned to specialized warning systems for both sea conditions and heavy rainfall, which can cause flash flooding and landslides in the hilly areas.
How the Weather "Feels"
Beyond the thermometer, the "RealFeel" in Chittagong is dictated by the dew point. For much of the year (April to October), dew points remain in the mid-to-upper 20s°C (70s°F), meaning the sweat does not evaporate easily. Locals adapt by favoring early morning activities and retreating indoors during the peak convection hours of the afternoon. In contrast, the winter sun is surprisingly strong despite the cooler air, often making it feel warmer than the reported temperature when standing in direct sunlight.