Jakarta's weather is defined by a tropical monsoon climate (Köppen Am), characterized by high temperatures and oppressive humidity that persist nearly 365 days a year. Because it sits just six degrees south of the equator, the city does not have "four seasons" in the traditional sense. Instead, life in the capital is dictated by the rhythm of the monsoons: the wet and the dry.
Typical Weather Patterns
The city's weather is remarkably stable in terms of temperature, generally fluctuating between 25°C (77°F) and 33°C (91°F). However, the real story is the rainfall.
- The Wet Season (October to April): Driven by the Northwest Monsoon, this period brings the heaviest rains. January and February are historically the peak months, often witnessing intense tropical downpours that can last for several hours or recur throughout the day.
- The Dry Season (May to September): Influenced by the Southeast Monsoon from Australia, this period is sunnier and considerably drier. While "dry" is relative—afternoon thunderstorms can still occur—the frequency of rain drops significantly, particularly in July and August.
Daily Climate Behavior
In Jakarta, the time of day often predicts the weather better than the month.
- Mornings: Often clear and relatively calm. This is when the air feels the "freshest," though humidity is at its peak (85–95%) at dawn.
- Afternoons: As the ground heats up, the atmosphere becomes unstable. During the wet season, this is the prime time for explosive convection, leading to thunderous downpours that can turn streets into rivers in minutes.
- Evenings: The rain often tapers off by late evening, leaving behind air that feels heavy and "sticky" as the moisture evaporates from the warm pavement.
Seasonal Trends & Unique Transitions
- The "Transitions" (Pancaroba): May and October are the transition months. These periods are notorious for unpredictable weather and particularly violent thunderstorms as the winds shift direction. Locals refer to this as musim pancaroba, a time when the sudden change in atmospheric pressure is traditionally believed to be a time of increased illness.
- The Peak of the Dry: August is typically the driest month. You will see more consistent blue skies, though the heat can feel more biting without the cooling effect of frequent rain.
Microclimates and Variations
There is a notable difference between North and South Jakarta.
- North Jakarta: Being coastal, it is slightly windier and subject to tidal flooding (Rob). This area experiences the "Urban Heat Island" effect more intensely due to high concrete density and lower elevation.
- South Jakarta: Closer to the foothills of the Bogor region, the South tends to be slightly greener and can receive more "spillover" rain from clouds that build up over the southern volcanic mountains.
Historical Context & Phenomena
Jakarta is a sinking city, which complicates its relationship with weather. Historically, major floods (Banjir) occur roughly every five to ten years (notable events in 2007, 2013, and 2020), usually triggered by the "Cold Surge" phenomenon—a blast of cold air from the North Pole that pushes moisture-rich clouds toward Java.
The Local Experience
Locals adapt to the rhythm of the city’s weather through a mix of high-tech and traditional means.
- The "Rubber Time" Mindset: During heavy rain, traffic in Jakarta (Macet) grinds to a halt. Locals often wait out the rain in one of the city's many massive air-conditioned malls, which serve as modern-day climate shelters.
- Pantau Banjir: Residents frequently use specialized apps (like JAKI) to monitor water levels at floodgates in real-time.
- Attire Adaptation: You will notice a preference for light, breathable fabrics. In the business districts, the formal Batik shirt is the standard, specifically designed to be appropriate for the heat while maintaining professional decorum.
What it "Feels Like"
In Jakarta, the "feels-like" temperature is the only number that matters. High humidity means that a 31°C day often feels like 38°C (100°F). The air is thick enough to feel "palpable" when you step out of an air-conditioned building. It is a sensory immersion: the smell of rain hitting hot asphalt, the sudden drop in temperature just before a storm, and the relentless intensity of the midday equatorial sun.