Phnom Penh Weather Guide: Tropical Seasons & Local Climate

Phnom Penh is characterized by a tropical monsoon climate that dictates the rhythm of life in the capital. The city sits in the low-lying central plains of Cambodia, a geography that traps heat and moisture, leading to consistent warmth throughout the year. The weather is defined by two primary monsoons: the dry northeast monsoon and the wet southwest monsoon.

The Three Distinct Phases of the Year

While technically divided into wet and dry seasons, locals and long-term residents identify three distinct climatic phases:

• The Cool Season (November to February): This is the most temperate time in the capital. Transitioning from the rainy season, the air becomes significantly less humid, and the skies clear. Daytime highs hover around 30°C (86°F), but the real difference is felt at night and in the early mornings, when temperatures can dip to 22°C (72°F). On rare occasions, cold fronts from the north can bring temperatures as low as 18°C (64°F), which locals treat as a significant cold spell.
• The Hot Season (March to May): As the northeast monsoon fades, the heat intensifies. This is the most challenging time for climate comfort. Temperatures regularly exceed 35°C (95°F) and can peak at 40°C (104°F) in April. The humidity builds steadily during these months, and the absence of wind creates an oppressive "stillness" in the air. Dust is common in the city during this time, and the landscape turns from lush green to a parched brown.
• The Rainy Season (June to October): Driven by the southwest monsoon, this season brings relief from the extreme heat but introduces high humidity and frequent precipitation. September and October are the wettest months. Rain typically follows a predictable daily cycle: bright, humid mornings followed by a buildup of dark clouds in the mid-afternoon, culminating in a violent but brief tropical downpour.

Daily Weather Rhythm

In Phnom Penh, the climate behaves with remarkable consistency. During the rainy season, mornings are often deceptively sunny. By 2:00 PM or 3:00 PM, the "afternoon storm" arrives—a signature phenomenon where the sky turns deep gray and torrential rain falls for 60 to 90 minutes. These storms are often accompanied by dramatic lightning.

During the hot season, the heat peaks around 1:00 PM and lingers long into the evening. The city's concrete and asphalt create an urban heat island effect, meaning the city center remains several degrees warmer at night than the surrounding rural provinces.

Local Adaptations and Experience

Residents of Phnom Penh have deeply adapted to these shifts. During the hot season, the city experiences a mid-day lull as people stay indoors to avoid the peak solar radiation. Conversely, during the rainy season, the city is prepared for "flash flooding." Because of the volume of water that falls in a short time, streets in lower-lying districts like Daun Penh or Boeung Keng Kang can flood ankle-deep within minutes. This water usually recedes just as quickly as it arrived, thanks to the city's improving drainage systems.

Locals often wear long sleeves even in the heat to protect against the sun, and the arrival of the "cool" season is celebrated, with many people donning jackets and sweaters the moment the thermometer drops below 25°C (77°F).

Atmospheric Sensation

The weather in Phnom Penh "feels" thick. Except for the peak of the cool season, the dew point remains high, meaning sweat does not evaporate quickly. Beyond the raw numbers on a thermometer, the heat index (what it "feels like") is often 5°C to 8°C higher than the actual temperature. During the transition into the rainy season, the air feels heavy and "charged" before a storm, a distinct olfactory and physical sensation that locals recognize as the imminent arrival of the monsoon.