How Much Does It Rain and What Temperatures Prevail in the US Virgin Islands?

The EnviroAtlas project provides a climate map based on PRISM data, which compiles 30‑year (1971‑2000) averages of rainfall and temperature for the US Virgin Islands. According to these figures, the islands receive roughly 1,500 mm of rain per year, split into a drier season from December to April and a wetter one from May to November. Average minimum temperatures hover around 22 °C, while maximums reach about 31 °C, creating a warm, humid tropical climate year‑round. These climate “normals” are essential for understanding how local weather shapes agriculture, tourism, and biodiversity. They also serve as a baseline to compare recent changes linked to climate change. If rainfall increases or temperatures rise, marine and terrestrial ecosystems could face stress, affecting coral reefs, forests, and water resources. PRISM data, derived from a network of weather stations and advanced interpolation algorithms, offers a solid foundation for planning adaptation strategies and educating young people about the importance of local climatology.

The PRISM (Parameter‑elevation Regressions on Independent Slopes Model) dataset was created by the PRISM Climate Group at the University of Oregon to deliver high‑resolution spatial climate estimates across the United States. The model merges observational data from weather stations with topographic variables (elevation, aspect, distance to the sea) using localized regressions, thereby reducing interpolation errors common in simpler methods. For the US Virgin Islands, station coverage is sparser than on the mainland, yet PRISM still incorporates the available observations, supplementing them with satellite data and surface models. The 30‑year climate normals (1971‑2000) represent the arithmetic mean of monthly precipitation and temperature values calculated over three decades to smooth out inter‑annual variability. These normals are essential for defining reference thresholds in ecological studies, water‑resource management, and climate impact assessments. Nonetheless, limitations exist: the spatial resolution (approximately 4 km) may miss island microclimates, and the 30‑year averages do not capture recent extreme events such as intensified heatwaves or hurricanes. For more up‑to‑date analyses, researchers should compare the normals with newer datasets (e.g., 1991‑2020) or regional climate model time series. Moreover, combining PRISM with other datasets (e.g., NOAA, NASA) enables validation and refinement of estimates, enhancing the robustness of scientific conclusions. In summary, PRISM offers a reliable foundation for understanding the historical climate of the US Virgin Islands, but scholars need to integrate these data with recent observations and extreme‑event analyses to fully assess ongoing climate change.