The Northern Mariana Islands experience a tropical rainforest type of climate (Köppen climate classification Af) with abundant rainfall. The climate is equable throughout the year, with little seasonal variation in temperatures. The Northern Mariana Islands constitute a United States territory that lies in Micronesia in the northwestern Pacific Ocean. The vast ocean, tropical latitudes, and trade winds dominate the climate of the islands. Typhoons present a significant threat year-round but frequently occur during the rainy season.
Northern Mariana Islands lie 15°to the north of the equator in the Mariana archipelago and experience sunny days throughout the year. Fourteen islands constitute the commonwealth, out of which Saipan, Tinian, and Rota are the largest. The islands lie in a general north-south direction, with Farallon de Pajaros at the extreme north and Rota in the extreme south. The northern islands are of volcanic origin, while the southern consists of limestone and coral reefs. Agrihan, Pagan, Anatahan, and other northern islands have active volcanoes. Mount Agrihan has the highest point on the islands, with an elevation of 965 meters.
The Northern Mariana Islands have pleasant weather for the majority of the year. Out of the two main seasons, the dry one lasts from December to June, while the wet season is from July to November. June temperatures are the highest during the year, while February is the coldest. Temperatures are rarely extreme and mostly average between 70°F (21.1°C) to 90°F (32.2°C). The temperatures rarely vary by more than 10°F (-12.2°C) between day and night, and there is little seasonal variation. The coldest temperatures average between 72°F (22.2°C) to 75°F (23.9°C) from December to February, while the hottest temperatures average between 83°F (28.3°C) to 85°F (29.4°C) from June to November.
Two-thirds of the year is wet, and even the dry season experiences significant rainfall with one-third of the annual rainfall. July to October is the rainiest period in the Northern Mariana Islands, which contributes to over fifty% of the yearly precipitation. The southernmost three islands in the chain are wetter than the rest, which see more rain on the slopes of the interior mountains. The annual sunshine lasts for 2200 hours, and the humidity is tenable even though the location is in the low latitudes. Days and nights are of roughly equal duration, and the rainfall is typical of the tropical islands of the Pacific Ocean. Northeasterly trade winds drive away the clouds during the dry season. Wind speeds mostly remain below an average speed of 20mph (32.2km/h).
The highest temperature on record for the Northern Mariana Islands is 90°F (32.2°C), while the record lowest temperature is 63°F (17.2°C).
The best time to visit Northern Mariana Islands
The best time to visit the Northern Mariana Islands is during the dry season from December to February when the precipitation is moderate. The coldest period of the year has pleasant temperatures that average between 73°F (22.8°C) to 81°F (27.2°C). March, in the second half of the dry season, is suitable for budget travelers than the first half. The sea temperatures are mild, and the conditions are calm. The relative humidity is less, which makes outdoor excursions enjoyable on the islands. Avoid Japanese national holidays during April and May as the visitor numbers peak during these months.
The worst time to visit Northern Mariana Islands
The worst time to visit the Northern Mariana Islands is between August to November when the typhoon season is at its peak. Hurricanes and tropical storms bring the destructive force of nature and often see winds above 100mph (160.9km/h) and huge tidal waves. The rainfall is intense, occurs almost every day, but rarely last for extended periods. The cloud cover sees an increase, as does the humidity and the heat index. August is the worst offender with the highest rainfall, humidity, and incidences of storms.
The Northern Mariana Islands are prone to thunderstorms, tropical cyclones, earthquakes, and volcanic eruptions. The Anatahan volcano is in an active state since May 2003, with an ejection of more than 50 million cubic feet of ash and rock. Volcanic smog, black clouds drift over to the southern islands of Saipan and Tinian many a time. The typhoon season lasts from August to January, with peak incidences from August to November. Thunderstorms are frequent, along with lightning and rain. Tropical storms bring heavy rains in the Northern Mariana Islands. The islands are prone to seismic activity and record moderate intensity earthquakes.
Weather in January
January is pleasant in the Northern Mariana Islands with blue skies welcoming the New Year. The daylight lasts for at least 11 hours, even during the relatively cold season. Turquoise blue waters await the tourists with miles of white, soft, sandy beaches that soothe the soul. The average temperatures in the modest range of 73°F (22.8°C) to 82°F (27.8°C) keep the atmosphere bright as the typhoon season ends. Cozy nights host food and fun fiestas for people of all ages. Saipan, the capital, has steady temperatures and languishing, tranquil waters suitable for scuba diving and snorkeling. Do not forget to bring water or rubber-soled shoes while going to the reef. Northeasterly winds drive away clouds as the precipitation registers less than 3.8" (96.5mm) in the month. Always expect rain, and carry at least a light rain jacket on the islands. Visitors from East Asia form a significant part of the tourist footfall in January in the Northern Mariana Islands.
Weather in February
February is the coldest month of the year in the Northern Mariana Islands, with the average temperatures remain in the 73°F (22.8°C) to 80°F (26.7°C) range. Clear, blue skies are the general theme except for short periods of rain, typical of the tropics. It is easy to wait out the wet spurts, and bask in the warm and bright sunshine on the beautiful beaches. Rota boasts of many beautiful villages with excellent food and festivities in the pleasant atmosphere of February. Sea temperatures usually are below 81°F (27.2°C), which are mild compared to the icy waters of the North Atlantic in the winter. Expect busy streets with plenty of visitors on the islands during the peak of the tourist season. Rental bikes and boats make it easy to explore the islands but carry a rain jacket for safety. Warm winter clothes are rarely useful on the Northern Mariana Islands even when the temperatures are at the lowest of the year.
Weather in March
March is as dry as it can get ever become in the year in the Northern Mariana Islands with only 2.4" (61mm) of rainfall. However, one out of every two days receives at least light showers. The directly overhead sun casts bright light that lasts for 7 hours within the 12-hour days. The average temperatures register in the 73°F (22.8°C) to 80°F (26.7°C) range, with moderate humidity and low wind speeds. The conditions are perfect for outdoor adventures, including off-road buggy tours and downhill biking. March is an excellent time of the year for a sunset dinner cruise in the Marina archipelago. Wear sunglasses and broad-brimmed hats while exploring the various outdoor attractions as the ultraviolet rays of the sun are at the highest degree. Expect afternoons to be hot and humid much of the time. March is an excellent time to visit the Northern Mariana Islands with comfortable conditions post the peak tourist season.
Weather in April
April is slightly wet in the dry season in the Northern Mariana Islands with an average of 5" (127mm) of rainfall. The average temperatures are in the 74°F (23.3°C) to 83°F (28.3°C) with 7 hours of bright sunshine and relative humidity less than 75%. The mostly clear skies extend the visibility beyond 6 to 8 miles on land as well as sea. The sunny days are perfect for scuba diving along Saipan's northeast coast or swim in the clear waters of the coral-filled Managaha islet. Wind speeds at Tinian International Airport frequently register in the 15 to 20mph (32.2km/h) range. The cliffs on the islands provide a 360-degree view of the surrounding landscape, and some of them have memorials from famous battles. Expect rain in the afternoons. April is usually a favorable time to visit the Northern Mariana Islands for those who do not mind a little rain.
Weather in May
May is hot in the Northern Mariana Islands with the average temperatures in the 76°F (24.4°C) to 84°F (28.9°C) range. The sunlight is intense, and sunscreen becomes mandatory as the ultraviolet rays reach dangerous proportions. The light precipitation lasts for short durations during the day and gives plenty of time to explore the islands on foot, bikes, or boats. The tranquil and clear waters are home to diverse marine species that are a unique part of the ecosystem. Expect temperatures to rise gradually with an increase in the heat index. Evenings are more comfortable with an occasional gentle breeze near the coast, while the nights are cozy. Light summer clothing is desirable, along with a sun hat and a lightweight jacket. May is a great time to visit the Northern Mariana Islands with a moderate number of visitors, affordable rates, and bright light for taking clear pictures.
Weather in June
June is the driest month of the year in the Northern Mariana Islands with the average temperatures in the 75°F (23.9°C) to 85°F (29.4°C) range. Steep hills with forest cover and secluded beaches form parts of many islands with volcanic rocks shining in the blazing sun. The paths are safe in the dry season, and the canopy of the jungle offers protection from the intense sun rays. Low tides give walking access to nearby offshore islands. Abundant fish and birds inhabit the islands and the surrounding tropical waters with no fear from humans due to protected environments. Take advantage of the long days by using mornings and evenings for outdoor activities. Afternoons are hot and usually better to spend in the comfort of the shade. The precipitation begins to register a gradual increase by the end of June in the Northern Mariana Islands.
Weather in July
July is the beginning of the wet season in the Northern Mariana Islands that sees up to 10.2" (259.1mm) of rain. The average temperatures are in the warm 75°F (23.9°C) to 84°F (28.9°C) range. However, the increased cloud cover and humidity raise the heat index. It rains almost every day, but the showers rarely last for extended periods, and there is no shortage of sunshine. The hill paths become slippery and muddy and treacherous to ascend. Trade winds lose strength as clouds dominate the skies, especially during the afternoons. Sea temperatures are at the highest of the year, yet the waters are mild and suitable for water activities. The longest days of the year ensure there is plenty of daylight during the evenings for fun-filled activities. Thunderstorms are frequent with occasional lightning and heavy rain. Watch out for storms as the typhoon season begins in July in the Northern Mariana Islands.
Weather in August
August is the wettest month of the year in the Northern Mariana Islands with an average of 12.4" (315mm) of rainfall. It rains cats and dogs, yet there are clear, extended periods of bright sunshine that last up to 5 hours a day. Day temperatures scale up to an average of 84°F (28.9°C), while nights register up to 75°F (23.9°C). The increase in humidity is the time for wearing sweatshirts and rain jackets for the remaining population on the islands. Sightseeing tours often face challenges with the decrease in visibility due to cloud cover and rain. Beach and snorkeling activities are best on sunny days. The American Memorial Park in Garapan draws a considerable number of visitors during rainy days. Always carry rain protection in the wet season when outdoors. It is prudent to avoid August if a trip to the Northern Mariana Islands is on the radar.
Weather in September
September is hot and humid in the Northern Mariana Islands with daily showers in Saipan, Tinian, and Rota. The average precipitation is 10.7" (271.8mm) in the month, with periods of heavy rain. The humidity is above 80%, and the average temperatures register between 75°F (23.9°C) and 84°F (28.9°C). The cloud cover is heavy in the absence of the northeasterly trade winds and restricts the sunlight to 5 hours a day. Hurricanes and tropical storms frequently visit the coasts and even raid the interior lands. Green sea turtles are a common nesting species on the soft coastal sands during the rainy months. Tourist numbers are low during the wet season and open up opportunities for budget travelers. Expect plenty of rain in the forests and on mountain slopes that make paths slippery and muddy. The Northern Mariana Islands wear a cloak of greenery in September.
Weather in October
October brings a massive 11" (279.4mm) of rain in the Northern Mariana Islands, and there is a rare day in the month that does not receive precipitation. The cloudy days limit visibility on the seas, and the slow tourist season affects the cruise business. The average temperatures remain in the range of 75°F (23.9°C) to 84°F (28.9°C) as the conditions remain sticky during both days and nights. Extreme temperatures are absent on the islands, and the record high for October is 88°F (31.1°C). Keep in mind that the sun rays are intense whenever they break the cloud cover. It is prudent to carry both a hat and a raincoat in the rainy season. Water activities see few takers, with the rain often playing a spoilsport. A few people visit Saipan for its history, museums, and monuments during the 12-hour days. The Northern Mariana Islands are generally short of visitors in October.
Weather in November
November sees a slight drop in temperatures and precipitation in the Northern Mariana Islands, with partly cloudy skies. The sunshine lasts for 6 hours a day as the rainy season is on its last legs. The average humidity drops below 80%, and the temperatures range between 75°F (23.9°C) to 83°F (28.3°C). Small farms begin to produce coconuts, melons, and breadfruit with the end of the wet season. Thunderstorms are frequent, and it is advisable to avoid afternoon excursions in the mountains. Gambling is a popular activity among tourists when diving and water activities are not feasible in the wet season. Wind speeds remain below 15mph (24.1km/h) except during typhoons and hurricanes when they frequently exceed 100mph (160.9km/h). Rain protection is mandatory as heavy downpours frequently occur, even though for short periods only. Tourist interest is lukewarm in the Northern Mariana Islands in November.
Weather in December
December begins the dry season in the Northern Mariana Islands, with the average temperatures in the 74°F (23.3°C) to 81°F (27.2°C) range. The atmosphere cools down a little, but there is hardly a winter season on the islands. Sunny days are common, and the 11-hour days receive more than 5 hours of bright sunlight. The humidity is on the wane, along with the rain, which registers a moderate 5.9" (149.9mm) in the month. Christmas and the arrival of the New Year see a rise in tourist footprint, mainly from Asia and North America. Seawater temperatures rise above 82°F (27.8°C), and the calm waters see a renewed interest in snorkeling and scuba diving. Carry a scarf, hat, and rain jacket for the probability of an all-weather scenario during the transition to the dry season. Keep an eye on the weather for storms that arrive at the end of the season. The mild weather in the Northern Mariana Islands in December is a precursor for the pleasant season ahead.