The surrounding municipality has an area of 12,206.18 km² and is one of the largest in the state. Besides the municipal seat the settlements are: Bahía San Carlos, Pueblo Vícam, San Ignacio Río Muerto, Pótam, Bahía de Los Lobos and Ortíz.
Guaymas is the second-largest port on Mexico's Pacific Coast (after Manzanillo). It is one of the major shrimp producing cities of northern Mexico and was formerly a major oyster producer, although pollution and overfishing have depleted its stocks greatly.
Guaymas is located in a semi-arid flat area. The climate is dry and very hot, with an average monthly maximum temperature of 31°C in the months of July and August and an average monthly minimum temperature of 18.0º in the months of January and February. The average annual temperature is 19°C. 
In a tradition dating back to 1888, one of Mexico's liveliest carnivals takes place on the waterfront every spring.
In June 2007, local mining conglomerate Grupo Mexico announced plans to build a copper smelter and refinery and a 400MW power plant at Guaymas.
The port was attacked by the French on two occasions in the 19th century: in 1854, José María Yáñez successfully led the townsfolk in repelling a group of filibusters under Gaston Rousset Bourbon and, in 1865, a flotilla of French ships took the port and occupied it until September 1866.
A fascinating account of life in Guaymas in the late 1960s / early 1970s from the point of view of a young American graduate student can be found in the book The Guaymas Chronicles by David E. Stuart. He reveals much of the lives of the poorer citizens of Guaymas as he describes his gradual integration into local society and the strong life changing friendships he made. In a sequel Guaymas Chronicles II, Zona Rosa, David E. Stuart returns to Guaymas and looks up many of his old friends from the first book after many years pass.