Arcata (originally Union Town or Union) is a city adjacent to the Arcata Bay (northern) portion of Humboldt Bay in Humboldt County, California, United States.  At the 2010 census, Arcata's population was 17,231.  Arcata, located 280 miles north of San Francisco (via Highway 101), is home to Humboldt State University.  Arcata is also the location of the Arcata Field Office of the Federal Bureau of Land Management, which is responsible for the administration of natural resources, lands, and mineral programs, including the Headwaters Forest, on approximately 200,000 acres of public land in Northwestern California.  According to the United States Census Bureau, the city has a total area of 11.0 square miles (28.5 km2), of which 9.1 square miles is land and 1.9 square miles (17.25%) is water.

Arcata contains public and shopping areas within the city.  They include the Downtown/Plaza Area, Northtown, and Valley West (each of these are also large neighborhoods). There are additional named neighborhoods encompassed by the city, including Aldergrove, Alliance (which was once a separate community located North of Arcata), Arcata Bottoms, portions of Bayside (despite it having its own Post Office and postal code), Bayview, California Heights, Fickle Hill (lower portions), Greenview, South G Street, Redwood Park (which includes the City owned Redwood forest), Sunny Brae, Sunset, and Westwood.  Arcata also contains the Arcata Marsh, a preserve located on the City's bay shore.

Arcata's climate is dominated by marine influences associated with Humboldt Bay and the Pacific Ocean.  On average, Arcata experiences 40 to 50 inches of rain per year, though there is a short but pronounced dry season from June to September.  Northerly winds keep the spring very cool and create a coastal upwelling of deep, cold ocean water.  This upwelling in turn results in foggy conditions throughout the summer, with high temperatures commonly in the 50s and low 60s.  Yet, just a few miles inland, the temperatures may be up to 25 degrees warmer in the summer and fall.  Winter high temperatures average in the low 40s to mid-50s, with lows in the mid-30s to lower 40s.  Temperatures infrequently dip below 30°F in the winter, and nearly as infrequently climb above 72°F in the summer and fall.