Vitals: Temperature
Water temperature affects all creatures living in the stream, as well as directly influencing water chemistry (including conductivity and dissolved oxygen. Different animals have different preferred temperature ranges; cold water fish such as rainbow trout like water to be less than 16°C, although they can tolerate higher temperatures. Deep, fast-moving, and shaded streams tend to be colder than shallow, slow-moving, and exposed streams.
Temperature should be below 24 Deg C
This is the maximum temperature tolerated by salmonids, although they tend to avoid waters that are over 20 degrees C. (Source: California Water Boards Temperature Threshold)