El Yunque National Forest, the only tropical rainforest in the U.S. National Forest System, is defined by its constant moisture, high humidity, and a climate that shifts dramatically with elevation. Located on the slopes of the Sierra de Luquillo, this 28,000-acre ecosystem acts as a biological engine, fueled by the Puerto Rican trade winds. These winds carry warm, moist Caribbean air that is forced upward by the mountains, cooling and condensing into near-constant rainfall.
Typical Weather Patterns and Daily Rhythms
There is no true "dry" day in El Yunque; rain is expected nearly every afternoon. The forest typically experiences a predictable daily cycle. Mornings often begin with soft light and broken cloud cover, offering the clearest views from peaks like Mt. Britton. As the tropical sun warms the lower elevations, moisture rises (a process known as orographic lift), leading to building cloud cover by midday and passing showers in the afternoon. These showers are often brief but can be intense, frequently followed by rapid clearing.
Seasonal Trends
While the temperature stays relatively consistent, the precipitation patterns create a distinct division between the High and Low seasons:
- The Drier Season (December – April): Despite being the driest window, showers still occur daily. During these months, humidity is at its lowest annual levels, and temperatures are more stable. This is the peak season for visitors, as trails are less muddy and the air feels significantly more manageable.
- The Wet and Hurricane Season (May – November): Rainfall increases, particularly in May and September. This period coincides with the Atlantic hurricane season (June 1–November 30). While major hurricanes are statistically rare, they are high-impact events that can cause forest closures. The forest is at its most lush and verdant during these months, and waterfalls like La Mina operate at peak power.
Microclimates and Elevation Changes
Temperature and rainfall vary significantly based on your height above sea level:
- Lower Elevations (Tabonuco Forest): Warm and humid, these areas feel much like the coastal towns of Río Grande. Daytime temperatures frequently hover around 85°F (29°C).
- Higher Peaks (Dwarf or Cloud Forests): Above 2,500 feet, the climate shifts toward a subtropical highland profile. At the summits, it is markedly cooler—often 10°F to 15°F lower than the base. In winter, night temperatures can drop into the 50s°F (10°C–15°C). The peaks are often engulfed in a permanent shroud of mist, with humidity levels reaching 100% as you walk through literal clouds.
What the Weather "Feels Like"
In El Yunque, the