Siem Reap Weather Guide: Climate & Seasonal Patterns

Siem Reap is characterized by a tropical savanna climate, marked by distinct wet and dry seasons driven by the alternating monsoon winds. The region remains warm throughout the year, but the experience of that heat shifts significantly depending on humidity levels and rainfall patterns.

Typical Weather Patterns

The year is divided into two primary meteorological cycles: the Northeast Monsoon (Dry Season) and the Southwest Monsoon (Wet Season).

• Dry Season (November – April): This period is dominated by clear skies and steady winds from the continent. Humidity is at its lowest, and rainfall is rare.
• Wet Season (May – October): Moist air from the Indian Ocean brings high humidity and regular precipitation. While the term "monsoon" often suggests constant rain, in Siem Reap, it typically manifests as intense, short-lived afternoon downpours followed by sunshine.

Daily Climate Behavior

In Siem Reap, the day follows a predictable rhythm based on the season:

• Mornings: Even in the hot season, mornings before 9:00 AM provide a brief window of relative coolness. During the "winter" months (December-January), mornings can feel genuinely brisk, with temperatures dipping to 20°C (68°F).
• Mid-Day: Between 11:00 AM and 3:00 PM, the tropical sun is at its most intense. In the wet season, this is when humidity peaks, creating a "heavy" atmospheric feel.
• Afternoons: During the rainy season, the sky often darkens rapidly in the late afternoon, leading to a dramatic thunderstorm. These storms typically last 30 to 60 minutes and provide a significant, refreshing drop in temperature.

Seasonal Trends

• Cool & Dry (November – February): This is the most temperate time of year. Rainfall is almost non-existent in January, and the air is noticeably crisper.
• Hot & Transitional (March – May): Historically the most challenging months, temperatures can soar to 40°C (104°F) in April. The heat is dry at first but becomes increasingly muggy as the wet season approaches.
• Lush & Wet (June – October): The landscape transforms into a vibrant green. September and October are the wettest months, with the highest risk of localized flooding near the Siem Reap River.

Local Microclimates

The presence of the Tonle Sap Lake to the south and the Kulun Mountains to the north creates subtle variations. Areas within the thick forest canopy of the Angkor Archaeological Park can feel several degrees cooler than the paved streets of the city center due to shade and evapotranspiration from the dense vegetation. Conversely, the city's "urban heat island" effect makes the downtown area feel significantly warmer at night compared to the surrounding rural rice paddies.

Historical Context & Phenomena

Historically, the Siem Reap region was built around managing water, as seen in the vast barays (reservoirs) of the Khmer Empire. In recent years, the region has seen record-breaking heatwaves linked to El Niño patterns. A specific phenomenon to note is the "Mango Showers"—erratic, light rains that occur in March and April, signaling the approaching change in seasons and the ripening of local fruit.

The Local Experience

Locals adapt to the heat by adopting a split-schedule lifestyle. The city is most active at dawn and again after sunset, with a noticeable lull during the peak heat of the day. In the wet season, the rain is rarely seen as a hindrance; rather, it is welcomed for agriculture. You will often see locals pausing their commute under eaves for 20 minutes to wait out a torrential downpour, knowing it will pass quickly.

What it "Feels Like"

Beyond the numbers, Siem Reap’s weather is an sensory experience. During the peak dry season, the air carries a fine, red dust from the unpaved roads. In the wet season, the air has an earthy, "ozonic" scent immediately before a storm. The heat in April is "piercing," demanding shade, while the humidity in August makes the air feel "thick," where even a slight breeze feels like a relief.