Mosca, Colorado is a small unincorporated community located in Alamosa County. Situated in the San Luis Valley, it experiences a semi-arid climate characterized by cool winters and warm summers. Average temperatures range from the mid-20s °F in winter to the mid-80s °F in summer. Precipitation is relatively low throughout the year, with an annual average of around 7 inches, primarily occurring in the form of snow during winter months.

Hydrology in Mosca is primarily influenced by the nearby Rio Grande River and its tributaries. These water sources provide vital irrigation for the region's agricultural activities, including the cultivation of crops such as barley, potatoes, and alfalfa. The area is also famous for its vast sand dunes formed by wind-blown sand from the river's floodplain.

Outdoor enthusiasts visiting Mosca have various recreation opportunities to explore. The nearby Great Sand Dunes National Park and Preserve offers a unique experience of hiking on the tallest sand dunes in North America. Visitors can also enjoy sandboarding, camping, and wildlife watching in the park. Additionally, the Rio Grande National Forest, located to the west, provides opportunities for hiking, fishing, hunting, and camping in a picturesque mountainous setting.