Large-scale tourism drives the Commonwealth of the Northern Mariana Islands (CNMI) economy, and many tourists visit to see the natural beauty of the Northern Mariana Islands, which is highly dependent on climate. Small increases in temperatures could result in large impacts to coral reefs, and subsequent impacts to the marine and coastal environment. Landfills to support the increasing population on the island have resulted in groundwater contamination on Saipan, which could contribute to disease [4], and have conflicted with environmental conservation and endangered species protection [1]. There is recognition that environmental degradation and stressors will exacerbate the impacts from variations and changes in climate. CMNI is located in the infamous Typhoon Alley, directly north of Guam. This puts the territory at risk on a routine basis for very powerful storms [6]. On December 8 and 9, 2002, Rota, the southernmost island of the CNMI was hit by Supertyphoon Pongsona. The typhoon produced sustained winds of 78 mph (126 km/h) with gusts up to 85 mph (137 km/h). The combination of winds and other effects from the typhoon left about 200 families homeless. The typhoon produced a storm surge of 22 ft (6.7 m) at Songsong Village, the largest village on the island. The surge caused moderate beach erosion on the island, and destroyed a fuel pier and a loading pipeline. Additionally, the typhoon caused severe crop damage on the island. The typhoon resulted in over $30 million in damage (2002 USD) [2].
Destroyed wooden house and relatively unscathed reinforced concrete house in eastern Songsong Village, Rota, after Supertyphoon Pongsona. (Source: NOAA National Weather Service (NWS) Meteorological Assessment Team for Typhoon Pongsona, 2003. http://www.nws.noaa.gov/os/data/pdfs/Pongsona_assessment_Final.pdf)
Geography
The Northern Mariana Islands, together with Guam to the south, make up the Mariana Archipelago. The Northern Mariana Islands consist of fourteen islands in a chain running roughly north-south, spanning approximately 375 miles (604 km) [5]. The total land area is approximately 179 square miles (464 sq km). The southern islands are limestone with level terraces and fringing coral reefs, while the northern islands are volcanic [1]. The northern islands are all either uninhabited or only very lightly populated [5], and there are active volcanoes on three of the islands: Anatahan, Paga, and Agrihan. Anatahan Volcano started erupting very suddenly in 2003, and has continued to alternate between eruptive and calm periods ever since [4]. The three southern islands – Saipan, Tinian, and Rota – are the largest and most populated in the chain. These three islands account for 65% of CNMI’s land area, 99% of the population and almost all of the economic activity and energy use. The island of Saipan is the capital and government seat, the major business center, and the largest and most populated island [6], with more than 90% of the country’s population [4]. The Mariana Trench, located to the east of the Northern Mariana Islands, is the deepest point in the world’s oceans. The measurement from the floor of the Mariana Trench to the top of Mount Tapotchau on Saipan, the highest point in the CNMI, is 37,752 feet (in comparison, from sea level Mount Everest measures 29,028 feet) [5].
Climate
The Northern Mariana Islands are considered the sunniest islands in Micronesia [3], and the Guiness Book of World Records has listed Saipan as having the most equable climate in the world [4]. The islands have a tropical marine climate moderated by seasonal northeast trade winds from November to March and easterly winds from May to October. Average year-round temperature is 84° F (28.9 °C) with an average humidity of 79%. There is little seasonal temperature variation. Temperature, however, is affected by elevation; hence, the islands of Saipan and Rota show considerable temperature variations between the coastal and mountainous areas [5]. The dry season runs from December to June, and the rainy season from July to November [4]. Sometimes the islands experience droughts from low rainfall during the dry season [5], and have also experienced drought during strong ENSO events, although not as severely as many other islands in Micronesia. The CNMI is situated some 600 miles (966 km) east of an area in the western Pacific which is the breeding area of cyclonic disturbances. As a result the CNMI is in what is known as weather condition four at all times, which means that 40 mile (64 km) an hour winds are possible within 72 hours [5]. These cyclonic disturbances can quickly and sometimes unexpectedly develop into typhoon force winds of up to 120 miles (193 km) per hour or greater. Typhoon season runs from July to January, and the islands of the CNMI are usually subject to at least one typhoon each year [5]. Flooding and wind-damaged vegetation are a common result of frequent storms with winds above 60 mph (97 kph) [6].
For a comprehensive summary of the climate trends and future projections, and how climate change is affecting CNMI’s key sectors, see Climate Change in the Commonwealth of the Northern Mariana Islands: Indicators and Considerations for Key Sectors (January 2021). Hotter weather, stronger typhoons, coral reef death, and physical and mental health risks are among the major challenges detailed in the report. Threatened resources include high-value coastal infrastructure and the millions of dollars that ocean ecosystems add to the CNMI economy annually. Climate change will disproportionately impact those who are already vulnerable, including children, the elderly, low-income families, and individuals with disabilities. Authors from the CNMI Office of Planning and Development, the National Oceanic and Atmospheric Administration’s Office for Coastal Management, and the East-West Center—along with 50 technical contributors from local governments, NGOs, researchers, and community groups—collaboratively developed the CNMI PIRCA report. Climate Change in the Commonwealth of the Northern Mariana Islands is one in a series of PIRCA reports aimed at assessing the state of knowledge about climate change indicators, impacts, and adaptive capacity of the US-Affiliated Pacific Islands and the Hawaiian archipelago.
Northern Mariana Islands
Commonwealth of the Northern Mariana Islands
Large-scale tourism drives the Commonwealth of the Northern Mariana Islands (CNMI) economy, and many tourists visit to see the natural beauty of the Northern Mariana Islands, which is highly dependent on climate. Small increases in temperatures could result in large impacts to coral reefs, and subsequent impacts to the marine and coastal environment. Landfills to support the increasing population on the island have resulted in groundwater contamination on Saipan, which could contribute to disease [4], and have conflicted with environmental conservation and endangered species protection [1]. There is recognition that environmental degradation and stressors will exacerbate the impacts from variations and changes in climate. CMNI is located in the infamous Typhoon Alley, directly north of Guam. This puts the territory at risk on a routine basis for very powerful storms [6]. On December 8 and 9, 2002, Rota, the southernmost island of the CNMI was hit by Supertyphoon Pongsona. The typhoon produced sustained winds of 78 mph (126 km/h) with gusts up to 85 mph (137 km/h). The combination of winds and other effects from the typhoon left about 200 families homeless. The typhoon produced a storm surge of 22 ft (6.7 m) at Songsong Village, the largest village on the island. The surge caused moderate beach erosion on the island, and destroyed a fuel pier and a loading pipeline. Additionally, the typhoon caused severe crop damage on the island. The typhoon resulted in over $30 million in damage (2002 USD) [2].
Geography
The Northern Mariana Islands, together with Guam to the south, make up the Mariana Archipelago. The Northern Mariana Islands consist of fourteen islands in a chain running roughly north-south, spanning approximately 375 miles (604 km) [5]. The total land area is approximately 179 square miles (464 sq km). The southern islands are limestone with level terraces and fringing coral reefs, while the northern islands are volcanic [1]. The northern islands are all either uninhabited or only very lightly populated [5], and there are active volcanoes on three of the islands: Anatahan, Paga, and Agrihan. Anatahan Volcano started erupting very suddenly in 2003, and has continued to alternate between eruptive and calm periods ever since [4]. The three southern islands – Saipan, Tinian, and Rota – are the largest and most populated in the chain. These three islands account for 65% of CNMI’s land area, 99% of the population and almost all of the economic activity and energy use. The island of Saipan is the capital and government seat, the major business center, and the largest and most populated island [6], with more than 90% of the country’s population [4]. The Mariana Trench, located to the east of the Northern Mariana Islands, is the deepest point in the world’s oceans. The measurement from the floor of the Mariana Trench to the top of Mount Tapotchau on Saipan, the highest point in the CNMI, is 37,752 feet (in comparison, from sea level Mount Everest measures 29,028 feet) [5].
Climate
The Northern Mariana Islands are considered the sunniest islands in Micronesia [3], and the Guiness Book of World Records has listed Saipan as having the most equable climate in the world [4]. The islands have a tropical marine climate moderated by seasonal northeast trade winds from November to March and easterly winds from May to October. Average year-round temperature is 84° F (28.9 °C) with an average humidity of 79%. There is little seasonal temperature variation. Temperature, however, is affected by elevation; hence, the islands of Saipan and Rota show considerable temperature variations between the coastal and mountainous areas [5]. The dry season runs from December to June, and the rainy season from July to November [4]. Sometimes the islands experience droughts from low rainfall during the dry season [5], and have also experienced drought during strong ENSO events, although not as severely as many other islands in Micronesia. The CNMI is situated some 600 miles (966 km) east of an area in the western Pacific which is the breeding area of cyclonic disturbances. As a result the CNMI is in what is known as weather condition four at all times, which means that 40 mile (64 km) an hour winds are possible within 72 hours [5]. These cyclonic disturbances can quickly and sometimes unexpectedly develop into typhoon force winds of up to 120 miles (193 km) per hour or greater. Typhoon season runs from July to January, and the islands of the CNMI are usually subject to at least one typhoon each year [5]. Flooding and wind-damaged vegetation are a common result of frequent storms with winds above 60 mph (97 kph) [6].
For a comprehensive summary of the climate trends and future projections, and how climate change is affecting CNMI’s key sectors, see Climate Change in the Commonwealth of the Northern Mariana Islands: Indicators and Considerations for Key Sectors (January 2021). Hotter weather, stronger typhoons, coral reef death, and physical and mental health risks are among the major challenges detailed in the report. Threatened resources include high-value coastal infrastructure and the millions of dollars that ocean ecosystems add to the CNMI economy annually. Climate change will disproportionately impact those who are already vulnerable, including children, the elderly, low-income families, and individuals with disabilities. Authors from the CNMI Office of Planning and Development, the National Oceanic and Atmospheric Administration’s Office for Coastal Management, and the East-West Center—along with 50 technical contributors from local governments, NGOs, researchers, and community groups—collaboratively developed the CNMI PIRCA report. Climate Change in the Commonwealth of the Northern Mariana Islands is one in a series of PIRCA reports aimed at assessing the state of knowledge about climate change indicators, impacts, and adaptive capacity of the US-Affiliated Pacific Islands and the Hawaiian archipelago.
Related Links
Latest Seasonal Rainfall Forecast for CNMI Rainfall variations during ENSOClimate Change in the Commonwealth of the Northern Mariana Islands: Indicators and Considerations for Key Sectors
National Weather Service Forecast Office Tiyan, Guam
Latest Seasonal Sea Level Forecast for CNMI
El Niño and its Impacts on Guam and the Commonwealth of the Northern Mariana Islands References [1]Pacific Data Hub, https://pacificdata.org/population-dashboard, accessed January 27, 2026.
[2] NOAA/NWS Meteorological Assessment for Typhoon Pongsona in: Pohnpei State, FSM; Chuuk State, FSM; Guam; and, Rota, CNMI. 2003. http://www.nws.noaa.gov/os/data/pdfs/Pongsona_assessment_Final.pdf, accessed May 5, 2021. [3] Shea, E., G. Dolcemascolo, C.L. Anderson, A. Barnston, C.P. Guard, M.P. Hamnett, S.T. Kubota, N. Lewis J. Loschnigg, & G. Meehl. 2001. Preparing for a Changing Climate: The Consequences of Climate Variability and Change for Pacific Islands. Honolulu: East-West Center, http://www.eastwestcenter.org/publications/preparing-changing-climate-potential-consequences-climate-variability-and-change-execut, accessed April 14, 2021. [4] Wikipedia, http://en.wikipedia.org/wiki/Northern_Mariana_Islands, accessed May 5, 2021. [5] The CMNI Guide, https://www.cnmi-guide.com/infos/, accessed April 14, 2021. [6] U.S. Department of Interior. 2006. United States of American Insular Energy Assessment Report 2006. Suva, Fiji: Pacific Power Association, www.doi.gov/oia/reports/upload/U-S-Insular-Area-Energy-Assessment-Report-2006.pdf, accessed May 5, 2021. [7] Wikipedia, http://en.wikipedia.org/wiki/Guam, accessed April 14, 2021.
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