Location

St. Croix is the southern and eastern-most of the U.S. Virgin Islands, lying 40 miles south of St. Thomas and St. John and separated from the rest of the Virgin Islands by an ocean trench 3,600 meters deep. It is the most easterly possession of the United States and lies about 100 miles south-southeast of San Juan, Puerto Rico. St. Croix is the largest and most agricultural of the 4 U.S. Virgin Islands, with a total area of 53,480 acres (85 square miles). St. Croix is approximately 22 miles long, east to west. The widest part of the west end of the island is about 6 miles, while the east end tapers to less than 1 mile in width, north to south. While St. Thomas, St. John and Water Island are part of the Puerto Rican geographical bank (the Greater Antilles), St. Croix is geographically located in the Lesser Antilles and lies completely within the Caribbean Sea.

Topography

St. Croix is characterized by a mountainous area in the northern part and a broad, rolling coastal plain in the southern part. The mountainous area is separated into east and west ranges by ancient marine sediments that extend in a southwest direction from an area near Christiansted and include the south-central and southwestern parts of St. Croix. The alluvium transported from these ranges is deposited in wide, frequently merging, alluvial fans that have buried ancient marine sediments at variable depths. More recent, exposed marine terraces are in the south-central, southwestern, and coastal areas, including the Frederiksted area.

The mountainous areas are characterized by numerous narrow, steep-sided valleys that have been cut by water flowing down the guts [intermittent streams], generally in a north to south direction. Mt. Eagle, which is in the western range, is the highest peak on St. Croix at an elevation of 1,165 feet above sea level.

The narrow coastal shelf surrounding St. Croix decends gradually, allowing for growth of a fringing reef along most of the shoreline.

Climate

St. Croix lies within the belt of subtropical, easterly tradewinds. The climate is maritime tropical and is characterized by generally fair weather, steady winds, and slight but regular annual, seasonal, and diurnal ranges in temperature. Rain-producing weather systems generally move into St. Croix from the east in summer and from the northwest in winter. From June through November, these weather systems are in the form of tropical waves that develop in the tropical Atlantic. Some of these waves develop into tropical storms or hurricanes, especially during August and September. The most recent hurricane to severely impact St. Croix was Hurricane Lenny in November of 1999. The risk of hurricanes striking St. Croix is about once every eighteen years. From December through May, St. Croix ’s weather-producing systems are frontal systems and low-pressure troughs that move in from the northwest. These frontal systems transport cold Canadian air into the Caribbean region.

Rainfall. Major rainfall events are associated with weather systems that enhance the uplift of moist air in the region. Orographic lifting of moist air over hilly terrain is the most common cause of rainfall in St. Croix. The amount of rainfall increases with increasing elevation. The total annual rainfall differs substantially at various locations throughout the island. The total annual rainfall is more than 50 inches in the northwestern part of the island, about 25 to 35 inches on the southwestern coast, about 40 to 50 inches on the south-central coast, and about 20 to 30 inches in the eastern part of the island. Leeward aspects receive greater amounts of rain because clouds develop over the slopes on a daily basis. In general, days have a higher incidence of rainfall than nights. St. Croix's wettest period generally is from September to November, and the driest period is from January to June. Occasionally, intense rainfall occurs during the drier period.

Temperature. The difference between the mean temperatures of the coolest and warmest months is only about 5 to 7 degrees F. The highest temperatures are in August or September, and the lowest are in January or February. During the warmest months, the highest average daytime temperature is about 88 degrees F. Warm spells can occur for short periods, and during this time the temperature can reach into the low 90’s for several days in succession. The average low nighttime temperatures during the warmest months are generally between 74 and 78 degrees F. During the coldest months, the highest temperature is generally in the low 80’s, and the lowest is in the high 60’s.

*information excerpted from the 1998 Soil Survey of the United States Virgin Islands.

Location of St. Croix in the Caribbean.