The National Park of American Samoa sits right in the heart of the South Pacific. Warm ocean waters and tropical trade winds shape a pretty unique weather environment year-round.
This remote paradise experiences a consistent tropical climate that influences every part of visiting this stunning destination. Warm temperatures hover between 77°F and 88°F all year, and two distinct seasons affect rainfall and humidity.
If you understand these weather patterns, you can plan a trip that makes the most of the park’s rainforests, coral reefs, and volcanic landscapes. From the intense wet season with its heavy downpours to drier months when trade winds bring some relief, American Samoa’s weather is a story of tropical extremes and natural rhythms.
You’ll want to keep these patterns in mind if you’re hiking muddy trails, snorkeling in clear waters, or just soaking up the island’s wild beauty—no matter what time of year you visit.
Overview of Climate in National Park of American Samoa
The National Park of American Samoa has a warm, humid tropical climate shaped by its spot in the South Pacific Ocean. Temperature doesn’t shift much, but two distinct seasons stand out, mostly because of rainfall patterns.
Geographical Location and Its Impact on Weather
The park sits in the South Pacific, between the Equator and the Tropic of Capricorn. That puts it straight in the tropical climate zone.
Because it’s south of the equator, its seasons run opposite to those in the northern hemisphere. When North America is chilly, American Samoa is deep into its wet summer.
Trade winds called “Malo’o” blow in from the southeast during the cooler months. They help keep temperatures in check and take the edge off the high humidity.
Volcanic mountains create big differences in rainfall from place to place. Higher spots get a lot more rain than the coast, thanks to moist air being pushed up and squeezed by the terrain.
Tropical Climate Characteristics
American Samoa has an equatorial climate—hot, humid, and rainy all year. Temperatures barely budge, but wet and dry periods still stand out.
The two main seasons:
- Wet summer season: October through May
- Drier season: June through September
Humidity stays high no matter when you visit. Rain showers are frequent and can last a few minutes or drag on for days.
Rainfall varies a lot from place to place. Drier coastal spots get around 125 inches per year, while the highest peaks can see up to 300 inches.
Typical Weather Year-Round
Temperatures stay pretty steady in the park. Daytime highs are usually in the high 70s to low 90s Fahrenheit.
From June to September—the drier season—average daytime temps run 79°F to 82°F. Nights can dip to 68°F to 72°F.
The wet season brings slightly warmer weather, but it rarely tops 90°F or drops below 74°F. Most of the time, you’ll see readings between 77°F and 88°F.
The Pacific Ocean keeps things stable, so you won’t get wild temperature swings like you might on the mainland.
Seasonal Weather Patterns
American Samoa National Park has two clear seasons, thanks to its tropical location. The wet season means heavy rainfall and high humidity, while the dry season brings cooler temps and less rain.
Wet Season: October to May
The wet season dominates most of the year—eight months of heavy rain and sticky air.
Temperature stays warm, with daytime highs in the high 80s to low 90s Fahrenheit. Nights don’t cool off much, usually staying above the upper 70s.
Rain showers hit often. They might last ten minutes or keep going for days. Some areas get quick afternoon downpours, others deal with steady rain.
Annual rainfall jumps during these months. Coastal and lower areas see about 125 inches a year, while the mountains can get up to 300 inches.
Humidity peaks, making the whole place feel steamy and lush.
Dry Season: June to September
The dry season offers a break from the rain. These four months are the best bet for outdoor adventures.
Temperatures drop just a bit. Daytime highs are 79°F to 82°F, with nights cooling to 68°F to 72°F.
Trade winds (“Malo’o”) pick up and help cut through the humidity. Hiking and exploring get a little easier.
Precipitation drops, but showers still pop up. They just don’t last as long or hit as hard as in the wet season.
Skies clear up, which is great for snorkeling and diving. More sun gets through to the reefs and trails.
Monthly Temperature and Precipitation Trends
Temperatures don’t swing much month to month—maybe 10-15 degrees Fahrenheit between the warmest and coolest times.
The hottest period is usually December through March, when both heat and humidity peak.
Rainfall changes a lot more than temperature. Wet months can bring three or four times as much rain as the dry ones.
The switch between seasons can get weird—sometimes gradual, sometimes sudden, depending on what’s happening in the region.
Even in the dry season, rain showers are common. There’s really no month without at least some rain in this climate.
Temperature and Humidity Throughout the Year
Temperatures in the park stick close to 77°F to 88°F, no matter the month. High humidity levels stick around all year, making the air feel warmer and heavier.
Average Highs and Lows by Month
Daily temperatures barely budge with the seasons. It’s rare for it to dip below 74°F or go above 90°F.
Summer months (October-May) are just a bit warmer, with highs in the mid-to-upper 80s.
Winter months (June-September) cool off a little, with highs usually in the low-to-mid 80s.
Nighttime temperatures stay warm too, with lows in the high 70s to low 80s.
The temperature range between seasons is tight—just 5-7 degrees Fahrenheit. No matter when you visit, you’re getting warm weather.
Mountain elevations cool off more than the coast. Higher spots can be a few degrees cooler, especially at night.
Humidity Levels and Their Effects
Humidity levels are always high—usually over 80 percent. The air feels muggy, and it can really sap your energy.
Heat index values often run 5-10 degrees hotter than the thermometer says. The mix of warmth and moisture makes everything feel stickier.
Mornings are often the muggiest. Overnight, moisture builds up, so after sunrise it can feel extra sticky.
Afternoons sometimes get a little relief when the trade winds pick up. Still, humidity rarely drops below 70 percent, even on the driest days.
Physical comfort can be tough for folks not used to the tropics. Sweat doesn’t evaporate as well, so cooling off isn’t easy.
Clothing choices matter here. Go for lightweight, breathable fabrics to stay as comfortable as possible.
Rainfall and Showers in the Park
The National Park of American Samoa gets a lot of rain, no matter the season. Rain showers are frequent, and some areas pick up over 300 inches a year, while drier places see about 125 inches.
Frequency and Duration of Showers
Rain showers hit often, and their timing is unpredictable. Sometimes it’s just a quick burst, other times it rains all day.
The tropical climate means precipitation can develop fast. You might get caught in a shower even if the sky looked clear an hour before.
High humidity helps showers form often. Weather can flip quickly—sunny one minute, heavy rain the next.
Showers can:
- Last minutes or hours
- Show up anytime, day or night
- Develop suddenly, with barely any warning
- Sometimes bring strong winds
Annual Rainfall Distribution
Two main seasons shape annual rainfall. Wet summer runs October through May, while the drier stretch is June through September.
Most rain falls during the wet season. December through March are usually the wettest months.
The dry season isn’t exactly bone-dry. Showers still show up, keeping the park lush and green.
Seasonal breakdown:
- Wet season (October-May): Heavy, frequent rain
- Dry season (June-September): Less rain, but still regular showers
- Peak rainfall: December through March
Regional Variations in Precipitation
Rainfall changes a lot depending on where you are. The park’s hills and valleys play a big part in who gets soaked.
Drier areas get about 125 inches per year, usually at lower elevations or in the rain shadow.
The highest mountains can rack up 300 inches or more. Elevation and wind exposure make a big difference.
Coastal regions see different patterns than inland spots. Mountains force air up, squeezing out more rain on the windward side.
Precipitation zones:
- Low elevation/dry areas: 125 inches per year
- Mountain peaks: Up to 300 inches
- Coastal regions: Varies with wind and exposure
- Windward slopes: Get the most rain
Notable Weather Features and Local Influences
American Samoa’s dramatic terrain creates weather that can change a lot over short distances. Mountain peaks over 1,700 feet act as barriers, trapping moisture and making rainfall jump by more than 175 inches from coast to highlands.
Role of Mountains and Elevation
Mountains shape the park’s weather in a big way. High peaks catch moisture-laden trade winds, pushing air up and squeezing out rain.
Coastal areas usually get about 125 inches of rain each year. The highest spots can see 300 inches—and that’s just a few miles apart.
Temperature drops with elevation too. The coast stays warm, but mountain peaks cool off, especially after dark.
Steep slopes cause orographic lifting. Trade winds slam into the mountains, rise, and dump rain, especially in the afternoon.
Microclimates Across the Park
Different parts of the park have their own weather quirks. Windward slopes get hammered by the trade winds and stay much wetter than sheltered spots.
Valleys and leeward sides of mountains are drier. Sometimes they’re surprisingly dry, even if a wet ridge is just a short walk away.
Forest canopy areas trap humidity, creating a greenhouse effect. Open grasslands and coastlines dry out faster after rain.
Beach and reef areas get constant ocean breezes. These spots have steady temperatures but high humidity, and salt spray from the waves changes which plants can grow near the shore.
Influence of Pago Pago and Coastal Areas
Pago Pago sits along the coast, and its location shapes the weather for much of the region. Even though it’s about 85 miles from the park, the city shares those same humid, tropical vibes.
Ocean temperatures don’t really dip much—they hover between 79°F and 84°F all year. This steady warmth keeps the air balmy and loads the atmosphere with moisture.
Trade winds sweep in from the southeast most of the year. These breezes pull in plenty of moisture from the Pacific, so you’ll feel that humidity.
Tides create quick shifts along the shore. When the tide’s high, cooler ocean water hugs the land. At low tide, coral reefs and tide pools soak up the sun and heat up fast.
Travel Tips for Visiting Based on Weather
American Samoa’s tropical climate demands a little extra planning if you want to enjoy the park. If you know what to expect and pack right, you’ll stay safer—and probably happier—while you’re here.
Best Times to Visit
The dry season runs from May through October. These months usually mean less rain and just a touch cooler air.
Temperatures don’t swing much—they stick to the high 70s to low 90s Fahrenheit. The wet season starts in October and stretches through May, with frequent rain showers and a muggy feel.
June through September is when the weather really shines. It’s the best window for hiking or snorkeling, in my opinion.
Rain during the wet season can hit hard and fast or stick around all day. Still, the heat doesn’t really let up, even when it’s pouring.
Recommended Clothing and Gear
You’ll want light, breathable clothes in American Samoa. Shorts, short-sleeved shirts, and sandals are usually enough for most days.
Rain gear is a smart move—those tropical showers can catch you off guard. But honestly, with the humidity, sometimes you feel just as drenched with or without a raincoat.
Bring sturdy boots if you’re hiking. Trails can get slick and muddy after it rains, and you don’t want to be slipping around.
In Samoan villages, wear modest clothing to fit in with local customs. Save the bikinis and tiny swim trunks for the beach.
A traditional lavalava isn’t just cultural—it’s actually comfortable in the heat. Both men and women wear these skirt-like wraps, and they just make sense here.
Weather-Related Safety Considerations
High humidity and temperatures can really up the risk of heat exhaustion. If you’re visiting, it’s smart to drink water often and rest in the shade when you can.
Muddy and slippery trails are probably the biggest weather hazard here. After it rains, hiking paths get especially tricky, so you’ll need to watch your step.
Sudden rain showers sometimes cut visibility and can cause flash flooding in low spots. It’s a good idea to keep an eye on the weather and skip stream crossings if it starts pouring.
The park gets anywhere from 125 to 300 inches of rain each year, depending on elevation. Mountain areas get drenched a lot more than the coast.
UV exposure stays high all year because of the tropical climate. Wearing sunscreen and protective clothing helps prevent sunburn, even when the sky looks cloudy.