The inter- and intra-annual evolution of temperature and salinity has been analyzed in the R¿as Baixas--ocean boundary. Each r¿a (Vigo, Pontevedra, and Arousa) is connected to the shelf by two entrances separated by islands. Samples were taken weekly at both mouths from October 1997 to October 2002. All r¿as are observed to share some common features: thermal inversion from November to February, intense upwelling events from April to September (observed in about 40% of the bottom measurement at the southern mouths), and the input of a warm water mass in October. The R¿as of Vigo and Pontevedra behave in a similar way, even quantitatively, and they differ slightly from the R¿a of Arousa. This difference is especially important at the northern mouth of Arousa, where water is fresher in winter and upwelling events are less frequent in summer. These differences are mainly due to the slightly different orientation of the R¿a of Arousa compared to the rest of the r¿as, the higher river discharge in this estuary, and the shallowness of its mouth.